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Clemson University 

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As the Nation's principal conservation Agency, the 
Department of the Interior has responsibility for 
most of our nationally owned public lands and 
natural resources. This includes fostering the wisest 
use of our land and water resources, protecting our 
fish and wildlife, preserving the environmental and 
cultural values of our national parks and historical 
places, and providing for the enjoyment of life 
through outdoor recreation. The Department 
assesses our energy and mineral resources and 
works to assure that their development is in the best 
interests of all our people. The Department also has 
a major responsibility for American Indian reservation 
communities and for people who live in island 
territories under U.S. administration. 

Front cover photo. 

Sandwich tern shading young 

on Sundown Island, Matagorda Bay, Texas. 

Photo by Kirke A. King 

Sport Fishery and 
Wildlife Research 


Activities in the Divisions of Research for 
the Fiscal Year 1975-76. 

Edited by 

Thomas G. Scott, Wildlife 
Helen C. Schultz, Wildlife 
Paul H. Eschmeyer, Fisheries 

Published by the U.S. Fish and Wildlife Service 
Printed by the U.S. Government Printing Office 
Denver, Colorado • 1978 


Foreword iv 

Sport Fishery and Wildlife Research 1 

Animal Damage Control 2 

Denver Wildlife Research Center 2 

Environmental Contaminant Evaluation — 15 

Fish-Pesticide Research Laboratory 15 

Great Lakes Fishery Laboratory 25 

Patuxent Wildlife Research Center 26 

Southeastern Fish Cultural Laboratory 34 

Coastal and Anadromous Fish 34 

Atlantic Salmon Investigations 34 

Eastern Fish Disease Laboratory 35 

Fish Control Laboratory 36 

Tunison Laboratory of Fish Nutrition 36 

Western Fish Disease Laboratory 37 

Endangered Species 40 

Patuxent Wildlife Research Center 40 

Pyramid Lake Project 45 

Great Lakes Fisheries 46 

Fish Control Laboratory 46 

Great Lakes Fishery Laboratory 47 

Tunison Laboratory of Fish Nutrition 57 

Inland Fisheries and Reservoir Management . 58 

Eastern Fish Disease Laboratory 58 

Fish Control Laboratory 61 

Fish Farming Experimental Station 64 

Fish Genetics Laboratory 66 

National Reservoir Research Program 67 

North Central Reservoir Investigations 68 

South Central Reservoir Investigations 70 

Southeast Reservoir Investigations 73 

Southeastern Fish Cultural Laboratory 75 

Tunison Laboratory of Fish Nutrition 76 

Western Fish Disease Laboratory 77 

Migratory Birds 78 

Migratory Bird and Habitat Research 

Laboratory 78 

National Fish and Wildlife Health Laboratory . 80 

National Fish and Wildlife Laboratory 83 

Northern Prairie Wildlife Research Center . . 84 

Patuxent Wildlife Research Center 89 

Mammals and Nonmigratory Birds 89 

Denver Wildlife Research Center 89 

National Fish and Wildlife Laboratory 95 

Cooperative Research Unit Program 97 

Cooperative Fishery Research Units 99 

Cooperative Wildlife Research Units 110 

Publications 121 

Appendix 139 

Reference to trade names does not imply Government endorsement of commercial products. 

The black-crowned night heron is commonly encountered during investigations of marsh ecology. Photo by J. T. 



A primary goal of the U.S. Fish and Wildlife Service is the 
conservation and sound management of sport fishery and 
wildlife resources for the benefit of present and future 
generations of Americans. Attainment of this goal requires the 
continual collection, analysis, and synthesis of new 
information on which wise and timely management decisions 
can be based. The Divisions of Research address the principal 
informational needs of the various management programs of 
the Service and provide many of the findings that contribute to 
the accomplishment of the Service's mission. 

This summary of the activities of the Research Divisions 
during the extended fiscal year 1976 (July 1, 1975 — 
September 30, 1976) provides an overview of the nature and 
scope of research completed and directs attention to the 
results that should be of significance in the management of 
fish and wildlife. 

A substantial portion of the research recounted here 
concerns cooperative studies between Service scientists and 
those of other Federal agencies, universities, State agencies, 
and other countries. We thank the many collaborators for their 
most valued assistance in advancing the Service's diverse 
research program. 


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Sport Fishery and 
Wildlife Research 

The research responsibilities of the Fish and 
Wildlife Service were carried out by four Divisions: 
Cooperative Research, Cultural Methods Research, 
Population Ecology Research, and Population 
Regulation Research. During fiscal year 1976, these 
Divisions continued to serve as the fact-finding arm 
of the Service. Information about species of fish 
and wildlife, the environments required for their 
existence, and the effects of management practices 
on them help the U.S. Fish and Wildlife Service and 
other government agencies to meet their respon- 
sibilities for conserving and managing the Nation's 
fish and wildlife for social, economic, aesthetic, and 
scientific benefits. In fulfilling the Service's research 
responsibilities, the Divisions cooperate with 
agencies of the Departments of Interior, Agriculture, 
Defense, and Health, Education, and Welfare; the 
Atomic Energy Commission; the Agency for 
International Development; the Environmental 
Protection Agency; and various State agencies, 
institutions, and private organizations. Completed 
research is communicated by talks and lectures, 
processed reports, and articles in popular and 
technical publications. A list of publications is 
provided in this report. 

During the fiscal year, research was carried out at 
25 major facilities, approximately 60 satellite field 
stations, and 45 Cooperative Research Units under 
the following programs: Animal Damage Control, 
Environmental Contaminant Evaluation, Coastal 
and Anadromous Fish, Endangered Species, Great 
Lakes Fisheries, Inland Fisheries and Reservoir 
Management, Land and Water Resources Develop- 
ment, Migratory Birds, Mammals and Nonmigratory 
Birds, Biological Services, and Cooperative Units. 
This alignment of programs permits the application 
of total agency resources to the attainment of 
specific objectives and encourages careful priority 
assessment of ongoing research programs. 

The planning, coordination, and administration 
of the research programs continue to be centralized 
in the Office of the Associate Director of 
Environment and Research in Washington, D.C. 
Fiscal, personnel, and property management and a 
variety of supporting services are provided the 
research facilities by the six Regional Offices of the 
Service. By the end of fiscal year 1976, the Divisions 
of Research had 730 full-time permanent employees. 
The budget included approximately $21,850,000 of 
appropriated funds and $3,150,000 of other funds. 

Animal Damage Control 


Sheep Losses on Selected Ranches in Southern 
Wyoming. — To help resolve conflicting claims 
about the severity of predator losses to the sheep 
industry, sheep losses from all causes were assessed 
on five southern Wyoming ranches during 1973-75. 
About 6,000 ewes and their lambs were monitored 
each year during spring lambing and the summer 
and winter grazing seasons. Lambs were much 
more vulnerable than ewes, and spring losses 
always exceeded summer and winter losses 
combined. Of 4,440 dead sheep examined, 
predators killed 1,030 or 23%. Predation was the 
largest single cause of death for lambs, but weather- 
related deaths from starvation, accidents, exposure, 
and disease, when combined, were greater in 
number. Most losses of ewes were caused by disease 
(26%) and predation (18%). During the 3 years, 
known predator kills were 0.2% of the ewes each 
year, and 1.5%, 2.1%, and 3.2%, respectively, of the 
lambs from the study herds. Coyotes caused 77% of 
the deaths from predation, black bears 11%, and 
golden eagles 9%. There were 1,232 ewes and lambs 
missing, mostly during summer, due mainly to 
miscounting and loose management by one ranch. 


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Neck wounds indicate that this lamb was killed by a 
coyote.The toxic collar seeks to exploit the coyote's 
typical throat attack pattern. Photo by G. E. Connolly. 

Losses of Sheep With No Protection from 
Predators. — Losses of sheep having no protection 
from predators were investigated on the Cook 
Ranch, Florence, Montana, March 15, 1974 to 
March 14, 1976. Coyote predation proved to be the 
primary cause of sheep losses, and predators killed 
more than 16% of the flock each year for a total of 

Coyote damage assessment studies to determine causes 
A pair of coyotes attacking an adult ewe. Photo by G. E. and time of sheep losses were conducted in several states. 
Connolly. Photo by S. B. Linhart. 

Coyote attractants are being evaluated by exposing them 
in small, plastic capsules and reading "sign" left at the 
"scent stations." Photo by F. J, Turkowski. 

1,027 sheep. Cause of death was undetermined for 
0.6% of the known losses the first year and for 0.8% 
the second year. Coyotes were responsible for 
97. 1% of the losses to predators the first year (first 
study) and 99.3% the second year. During the 
second year, 80.7% of the sheep taken by coyotes 
were killed by neck and throat wounds. Coyotes 
were sighted 61 times, dogs 3 times, and red foxes 2 
times. Of the 602 sheep killed by coyotes during the 
second year, scavenging birds fed so extensively on 
83 carcasses that the amount of feeding by coyotes 
could not be determined. Feeding was light to 
moderate on 401 of the other 519 carcasses, and 
return feeding was insignificant. Ewe lambs and 
twins were taken by coyotes more often than 
wethers and single lambs. 

Secondary losses, resulting from harassment by 
coyotes, included reduced lambing success, 
increased excitability of flocks, reduced growth 
rates, difficulty in fattening lambs, and loss of 
unborn lambs. 

Pneumonia, weak calf syndrome, and old age 
complications were the primary causes of natural 
deaths. Health of the sheep killed by coyotes was 
comparable to that of the rest of the herd. 

Success in controlling coyotes by M-44's, 
shooting from a helicopter, snares, experimental 
sodium cyanide collars, and a spray-on repellent 
was monitored. Conventional predator control 
methods killed 44 coyotes: 18 by M-44's, 23 by 
shooting from a helicopter, and 3 by snares. Three 
coyotes, radio-collared and tracked during the 
second year, were seldom found among the sheep. 
Predation was reduced but not stopped by the 
conventional controls used. 

Biologist examines coyote tracks at a scent station in 
Idaho. A new, synthetic scent developed by Denver 
Research Center chemists was used for the 5th annual 
survey of relative predator abundance in September 1976. 
Photo by G. E. Connolly. 

Annual Survey of Relative Predator Abundance. 

— The 1975 annual survey of relative predator 
abundance in the western United States showed a 
decline of 5% for coyotes as compared with 1974, at 
a lowered probability of 80%. The data are intended 
to reflect year-to-year changes in visitation indices 
for various predators, particularly coyotes, 
attracted to standardized scent-station lines. The 
method was not designed for estimation of numbers 
of animals per unit area, differences in abundance 
between species inhabiting the same area, or 
differences in relative numbers of a single species 
between areas, although some of these unwarranted 
interpretations appear in the Press. It is, however, 
intended to show year-to-year changes in trends, 
comparing lines sampled one year with those of the 
previous year. 

Analysis of the first 4 years of data (1972-75) 
indicates that the coyote visitation index for the 
western United States increased 10% between 1972 
and 1973, and again between 1973 and 1974. At a 
probability level (P) of 95%(5% risk of error), both 
changes were statistically significant. 

No significant changes occurred in the statewide 
coyote index for any individual state between 1974 
and 1975 at the 95% level of probability. Only in 
North Dakota (decrease of 27%, P - 85%) and in 
Iowa (increase of 49%, P - 90%) did changes in the 
visitation rate approach the 95% level of 
confidence. This lack of significant change may be 
due to the inherent variability in coyote response 
and /or insensitivity of the method, which can be 
compensated for by increasing the number of 
survey lines or by increasing visitation through the 

use of a better attractant. 

Most observers consider that the 10% increases 
(1972, 1973) followed by the 5% decrease (1975) 
reflect no major impact on coyote populations from 
control measures, the ban on toxicants, or rising fur 
prices, unless these factors somehow cancel each 

The Development of a Synthetic Coyote 
Attractant and Deer Repellent. — Field tests 
showing that the volatile components of a 
fermented egg formulation are attractive to coyotes 
and repellent to deer suggested that a dual-purpose 
synthetic mixture could be made from the 
important compounds in this material. Gas 
chromatography-mass spectrometry analyses were 
conducted, and 74 compounds were identified, 
including acids, alcohols, alkyl aromatics, esters, 
ketones, and terpenes. These compounds were 
combined in a stepwise process to form a synthetic 
mixture that elicited from coyotes and deer 
behavioral responses similar to those caused by the 
natural product. 

An important aspect of this work was the use of 
the human nose to eliminate much of the time- 
consuming and expensive behavioral testing on 
coyotes and deer. First, compounds were combined 
according to their relative concentrations in four 
fermented egg fractions, each of which had a 
different odor quality (fruity, fishy, sweaty, and 
sulfurous). The relative concentrations of these 
compounds were adjusted until the odor closely 
resembled natural fermented egg. An odor panel of 
18 persons (judges) was used for the final 
refinement of this mixture. Various modifications 
were compared with the natural product until a 
blend was achieved that produced a 40% error in 
discrimination by the judges. This blend was 
labeled synthetic fermented egg (SFE). 

In standardized tests at equivalent odor 
intensities SFE was statistically equal to the 
natural fermented egg in attracting coyotes and in 
repelling deer. The concentration in both cases can 
be increased over 40-fold. The final stage of 
development will involve the preparation of 
formulations of desired longevity and weather- 
ability for field applications. 

Predator Attractants Field Tested. — Few of the 
odor attractants that are used to lure predators to 
capture devices have been systematically tested for 
their effectiveness, species selectivity, or the type of 
response they elicit. Sonic and visual attractants 
have received only limited attention by researchers. 
Many attractants have been field tested in an effort 
to find more efficient and selective techniques for 

capturing predators. 

Odor attractants were tested by exposing plastic, 
disk-shaped capsules containing the lures. They 
were placed at 0.3-mile intervals along primitive 
ranch roads in random sequence. Predator visits 
were determined by observing tracks and sign 
present each day within a cleared area 3 feet in 
diameter around each capsule. Comparisons of 
behavioral responses and the numbers of visits to 
the lures indicated which were most attractive to 

Over 3,000 visits by coyotes to odor lures were 
recorded. Visits of other animals to the lures were 
also recorded. Data have also been accumulated for 
other animals. These visitors included raccoons, 
cattle, bobcats, rabbits, striped skunks, gray foxes, 
badgers, javelina, and horses. Numbers of visits 
fluctuated daily, probably because of environmental 
factors and differences in the behavior of the 
animals. Strong winds apparently reduced activity 
and the ability of predators to detect odor sources 
as there were fewer total visits on the windiest days. 
Behavior observed included urination, defecation, 
scratching, digging, biting, licking, pulling, 
carrying capsules, and rolling on the station. 

The results of one test phase indicated that a 
synthetic egg product was a good attractant — it 
elicited a high rate of visitation and numerous 
pulling and biting responses from coyotes. These 
properties show promise for use with existing 
operational techniques, and those developed by 
research. Additional field evaluation is planned. 

Ten sonic attractant test devices were constructed 
and field tested for durability and attractiveness to 
predators. These units were tested in the same 
manner as the odor attractants. Each electronic 
unit was powered by a 9-volt battery and was 
contained in a 1-pint metal can with a perforated 
top. When activated, the devices emitted sounds 
resembling those of prey animals. Five of the 
devices produced squeaking sounds similar to the 
distress calls of mice, and the remainder emitted 
sounds like the warblings of small birds. The 
warbling devices appeared to attract more 
predators than the "squeakers." Wind did not 
seriously decrease visits to the devices. The units are 
self-contained, appear weatherproof, and are 
durable and small enough to be easily transported 
and camouflaged. If the devices continue to show 
promise, they will be tested in combination with 
odor and visual attractants. 

Food Storage and Retrieval by Coyotes. — 
Observations of food storage and retrieval by 

penned coyotes near Logan, Utah, are providing 
information on these basic behavioral patterns. The 
specific behavior is complex but usually involves 
transporting the food to the caching site, digging a 
small depression, dropping the food in the 
depression, compacting it, and covering it by 
scraping loose soil, vegetation, or snow over it. The 
site may or may not be scent-marked by urination. 
To retrieve caches of food, coyotes carefully scratch 
away the cover, usually employing one foot at a 
time. Coyotes give concentrated attention to this 
task, smelling and watching the hole as they dig. 
When a portion of the cache becomes visible, the 
coyote snaps it up in its mouth, shakes it vigorously, 
and carries it off to eat. 

Food storage appears to be triggered by an 
abundance of food or by difficulties in feeding (e.g., 
long bones, skulls, or frozen carcasses). Storage not 
only saves food for later use but also enables 
coyotes to share an abundance of food, because one 
coyote's store is frequently recovered by another. 
At times it appears that habitual storage locations 
are used. The food-storing behavior of coyotes 
appears to be an innate, fixed pattern, for pups as 
young as 6 weeks old have performed this series of 
actions with no opportunity to observe the pattern 
in others. The same pattern has also been observed 
in kennels with concrete floors, where actual 
digging and covering were precluded. 

Evaluation of Fencing to Exclude Depredating 
Coyotes. — A 2.5-year contract with Oregon State 
University to evaluate electric and nonelectric 
fences to exclude coyotes from sheep pastures is 
nearing completion. Captive coyotes were trained 
to run a specific route within a large enclosure and 
various test fences were then placed across the 
coyotes' route of travel. In subsequent tests at 
Oregon State University and at the Service's 
Denver Center, captive coyotes were trained to kill 
live prey (rabbits), and then the coyotes and 
tethered rabbits were placed on opposite sides of 
test fences. 

The Oregon State study evaluated 34 con- 
figurations of electric and nonelectric fencing and 
made recommendations as to mesh size, height, 
overhangs, and aprons. The researchers found that 
electric fences usually did not deter captive coyotes 
from killing tethered prey and that wires could not 
be positioned in such a way that coyotes always 
received a shock. However, after certain modifi- 
cations, workers at the Denver Center found that a 
three-strand electric fence was effective in deterring 
captive coyotes from crossing to attack tethered 
rabbits. These studies have provided the data 

A trainer encouraging Komondor guard dogs to be 
aggressive towards coyotes. Training of these dogs to 
protect domestic sheep from coyote predation involved 
teaching them to respond to obedience commands, avoid 
harassment of sheep, be aggressive towards coyotes, and 
remain within fenced pastures with sheep. Photo by R. T. 

needed to undertake a field evaluation of fencing in 
the management of farm and semifarm flocks. 
Guard Dogs Protect Sheep from Coyotes. — A 

pilot study to determine whether Komondor guard 
dogs could reduce coyote predation upon domestic 
sheep has been completed. Four of the large (85- to 
120-pound), white, long-haired dogs underwent a 
four-stage training regime. The dogs were 
obedience-trained, paired with sheep to observe 
dog and sheep interactions, taught to respond 
aggressively to coyotes, and trained to remain 
within a fenced pasture. One field-test site in 
Montana and two in North Dakota were then 
selected, and coyote kills of sheep were documented 
for 20 days before placing a pair of dogs on a test 
site. The dogs remained on each test site for 20 days 
while damage assessment continued. The dogs were 
then removed and assessment of coyote kills 
continued for 20 additional days, after which the 
data were tabulated and summarized. 

Coyotes killed 50% to 75% fewer sheep when the 
dogs were present, indicating some potential for 
deterring coyote predation — at least for some farm 
and semifarm flocks. One pair of dogs began 
harassing sheep during the later stages of the 

Montana test and continued to do so despite a 
determined effort by the technician to halt this 
behavior. It is hoped that a different approach to 
the selection and training of the Komondors will 
prevent undesirable behavior in future tests. 

Coyote Mortality and Dispersal in South Texas. 
— Sixty-three coyotes were instrumented with 
mortality-sensing transmitters during the first 2 
weeks of November in 1974 and 1975 in Webb 
County, Texas, and 21 have been recovered as 
mortalities. Of these deaths, 71.2% were caused by 
man (gunshot, trap, vehicle), 14.3% were due to 
natural factors (malnutrition, mange, disease, or a 
combination of these), and 14.3% were from 
unknown causes (carcasses decomposed when 
located). The mortality rate of juveniles was 
significantly higher than that of adults. 

Dispersal occurred during the last 2 weeks of 
November. Juvenile females were the mobile 
segment of the population. Eight of the nine 
dispersing coyotes were juvenile females, and they 
moved an average distance of 21.5 miles. 
Dispersing juvenile females had a human-induced 
mortality rate double that of nondispersing 
juvenile females (50% and 25%). 

Control of Problem Coyotes by Toxic Collars on 
Sheep. — The toxic collar for sheep exploits the 
coyote's typical attack behavior by placing a 
toxicant-filled reservoir on sheep where it will be 
broken by attacking coyotes. The toxic collar is 
essentially a passive delivery system (in contrast to 
the M-44, which shoots sodium cyanide into the 
coyote's mouth), and the toxicant should not have 
aversive properties if a coyote is to self-administer a 
lethal dose. A polyvinylchloride collar filled with 
sodium cyanide, developed in 1975, killed 9 of 12 
coyotes attacking sheep in pen tests. In field tests 
during August and September 1975 in North 
Dakota, Montana, and Texas, 14 tethered lambs 
wearing similar collars were attacked by coyotes, 
and collars on 8 of the lambs were broken. None of 
the attacking coyotes was known to have been 
killed, suggesting that the caustic taste and strong 
odor of the poison repelled them. Research thus far 
indicates that the toxic collar will control problem 
coyotes if a suitable toxicant can be found. This 
method of control may be costly, limiting its use to 
problem coyotes that elude other controls. 

A search to find a more suitable toxicant has 
been under way since September 1975. The search 
involves literature review, consideration of specific 
chemicals within a given class, and consultation 
with representatives from industry and academic 

Tests of acute oral toxicity were conducted with 
1 1 of the hundreds of chemicals for which 
information was given. Of these 1 1 chemicals, it was 
determined that only 4 (diphacinone, mandelonitrile, 
4-aminopyridine, phosphamidon) merited testing 
in toxic collars with penned coyotes. Diphacinone, 
an odorless, tasteless oral anticoagulant used in 
rodenticide baits, was the only chemical that did 
not have offensive properties. In comparison 
studies of the effectiveness of the chemicals used in 
the collars, coyotes attacked sheep wearing either 
sodium cyanide or diphacinone collars. Puncture of 
collars containing sodium cyanide caused an 
abrupt cessation of the attack, whereas coyotes 
attacking sheep wearing diphacinone collars 
persisted in attack until the sheep were killed. 
Estimates of the volume of toxicant ingested by 
these coyotes showed that larger doses of 
diphacinone than of sodium cyanide were ingested. 
In field trials with diphacinone, many of the toxic 
packets had multiple punctures after an attack, 
indicating that diphacinone is not offensive to 
coyotes. In contrast, toxic collars containing 
sodium cyanide never had more than one packet 

Despite the nonaversive properties of diphacinone, 
the chemical has an important shortcoming — 
several days are required for a coyote to succumb to 
a lethal dose. A lethally dosed animal can continue 
to attack lambs before it dies. Thus, it is difficult to 
evaluate the efficacy of diphacinone for toxic 
collars in the field because of the long interval 
between dosing and death of the coyote. New 
(immigrating) depredating coyotes could enter the 
population as rapidly as the resident coyotes could 
be removed with diphacinone. 

Researchers unanimously agree that an odorless, 
tasteless chemical that produces mortality within 24 
hours is needed. The feasibility of microencapsulating 
cyanide chemicals to mask aversive properties is 
being investigated. Microencapsulation has not 
been uniformly successful in all chemical applications, 
but the technique may have utility for the toxic 
collar. The search for the ideal predicide for the 
toxic collar will continue, and additional sources 
that could supply such a chemical will be 

Expanding Collars for Wildlife Transmitters. — 
A collar attachment for wildlife transmitters has 
been developed that expands or contracts to fit an 
animal properly. Young animals can therefore be 
instrumented with no danger of outgrowing the 
collar. In a test, 1 -day-old domestic lambs were 
instrumented with expanding collars that incor- 

porated simulated transmitters weighing 60 g. A 
year later these collars were removed from the 
mature lambs. No abrasions or distressful effects on 
the animals were noted. This method of attachment 
can be used on deer, antelope, moose, and elk. 
Three types of mortality-sensing electronic circuits 
have now been designed for these expanding 

Hazards to Wildlife Associated with Rodenticide 
Baiting. — Under an Environmental Protection 
Agency (EPA) contract, the hazards associated 
with strychnine baiting for pocket gophers in 
Minnesota and for ground squirrels in Wyoming 
were evaluated. On the Sherburne National 
Wildlife Refuge, Minnesota, 1 ,638 acres were treated 
with a burrow-builder, using 0.5% strychnine- 
treated bait. Treated fields were scattered 
throughout 10 sections. Control was good — data 
from activity plots of pocket gophers showed 87.5% 
reduction in activity. Populations of other small 
rodents (quite low initially) declined significantly 
on the treated area but increased significantly on 
the control area. To measure secondary effects of 
strychnine, 36 raptors and 36 mammalian 
predators were equipped with radio transmitters but 
no effect was detected. Red-tailed hawks, American 
kestrels, great horned owls, badgers, striped 
skunks, a red fox, and a coyote were intensively 
radio-tracked during treatment; all those that used 
treated fields survived. Tracks and diggings of 
mammalian predators were frequently observed on 
the burrow-builder tracks after treatment. Red- 
winged blackbirds were selected as representatives 
of seed-eating birds, and 100 territorial males on 
both the treated and control areas were marked for 
monitoring during the treatment. Even though 
some treated grain was available on the surface, and 
marked birds were observed feeding in treated 
fields, only one bird, a mourning dove, was found 
killed by the treatment. 

In south-central Wyoming, approximately 9,000 
acres were baited with 0.5% strychnine-treated bait 
for controlling Richardson's ground squirrels. 
Approximately 1 tablespoon of bait was placed 
from horseback at or near each ground squirrel 
burrow. Effectiveness of the treatment varied; some 
study plots showed almost no control of ground 
squirrels and others indicated over 90% control. 
Many territorial horned larks in baited areas were 
killed by the treatment. Before treatment, 
territorial horned larks averaged two per acre. 
After treatment, an average of 1.5 dead horned 
larks were found per acre searched. Some red- 
winged blackbirds, Brewer's blackbirds, yellow- 

Richardson's ground squirrel. Ground squirrels, while an 
important food source to several avian and mammalian 
predators, can cause significant damage to agricultural 
crops. Photo by T. A. Gatz. 

headed blackbirds, and cowbirds were killed by the 
treatment. Bait was being distributed as some birds 
were migrating through the area, and dead 
blackbirds, especially red-winged and Brewer's 
were found on most plots. Red-winged and yellow- 
headed blackbirds were not totally annihilated in 
baited areas but were reduced in number. 
Telemetry indicated that at least some of the 
survivors were not feeding in baited areas. Average 
numbers of dead birds found per acre searched were 
0.5, 0.5, and 0.16 for red-winged, Brewer's, and 
yellow-headed blackbirds, respectively, and 0.05 
for cowbirds. Mourning doves did not arrive until 
early May, when baiting was well under way, but 
doves that fed in baited areas proved likely to be 
killed. Dead doves on most plots searched (average, 
0.35 dove per acre) and radiotelemetry data 
indicated that at least 25% of the radio-equipped 
doves died from eating the bait. Averages for other 
dead birds found per acre searched were 0.1 for 
vesper sparrows and 0.025 each for meadowlarks, 
starlings, savannah sparrows, and crows. The 
control program appeared to have no effect on 
raptors or mammalian carnivores. 

These studies indicate that strychnine bait 
properly applied with the burrow-builder for the 
control of pocket gophers is a relatively safe 
procedure with few hazards to nonrodent wildlife. 
However, strychnine bait applied to the surface 
near holes of ground squirrels kills many seed- 
eating birds. 

Antler Growth Suppressed by Diethylstilbestrol 
in White-tailed Deer. — Tube-type implants 
containing diethylstilbestrol (DES) were tested in 
male white-tailed deer as a method of controlling 
deer populations in National Parks. In mid-April 




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This map of the Buffalo Gap National Grasslands, South Dakota, shows changes in distribution, size, and number of 
prairie dog colonies from 1968 to 1975. The number of colonies increased from 114 in 1968 to 479 in 1975 while the 
acreage occupied went from 3,072 to 18,691. Photo by G. K. LaVoie. 

the implants were placed in the scrota. During the 
peak of the breeding season, mid-November, the 
animals were autopsied. 

DES drastically suppressed growth of antlers, 
but the velvet was shed and bone antler was formed. 
None of the antlers exceeded 5.4 cm in length, and 
the basal burrs failed to develop. Testicle weights of 
the treated deer were much less than those of similar 
untreated animals. Spermatogenesis was affected 
but the response was not uniform, ranging from 
almost complete cessation to limited sperm 
production. Cell loss appears to have occurred in 
the round spermatids. The number of round 
spermatids, as measured in stage I of an eight-stage 
cycle, averaged only 37.9 cells for treated animals 
compared with 131.6 cells for untreated animals. 

The abnormal antler development is aesthetically 
unacceptable; therefore, no additional research 
with DES implants on male white-tailed deer is 

Colony Expansion by Prairie Dogs Traced by 
Remote Sensing. — Remote sensing is being used 
to study expansion of prairie dog colonies. Aerial 
photographs have been taken each year to 
determine annual changes in number, size, and 
distribution of prairie dog colonies on 400 square 
miles of the Buffalo Gap National Grasslands, 
South Dakota. In photographs, taken at a scale of 
1 : 1 5,840, individual prairie dog mounds are readily 
visible. Standard photogrammetric techniques are 
used to plot and measure colonies. 

The number of prairie dog colonies has increased 
dramatically in the past 7 years. There were 114 
colonies in 1968, 178 in 1974, and 479 in 1975. The 
area occupied by prairie dogs has also increased 
from 3,072 acres in 1968 to 18,691 in 1975. 

Aerial photography is far more economical than 
ground censuses. The cost for a photo run and 
contact prints averaged only lc per acre for the 
South Dakota study. 

Florida Water Rat Well-established in Florida 
Sugarcane. — In cooperation with the Florida 
Sugar Cane League and the Virginia Cooperative 
Wildlife Research Unit, the distribution and 
depredations of the Florida water rat are being 
studied in southern Florida. It is one of several rat 
species that damage Florida sugarcane. It lives in 
distinct burrow systems irregularly scattered in 
infested sugarcane fields of about 35 acres each. In 
January-March 1976, a survey of its distribution 
and relative abundance was conducted on lands of 
the Western Division of the U.S. Sugar Corporation, 
which represents about 10.8% of Florida's 
sugarcane crop. Approximately 26% (237 fields) of 
all fields harvested in the Western Division area 
were selected at random and were examined for 
presence of burrows. Forty-one percent of the fields 
showed evidence of burrowing activity. The mean 
number of burrow systems per acre in infested fields 
was 0.28 (range, 0.02-1.39). 

Vampire Bat Control and Paralytic Rabies. — 
Parasitism on cattle by vampire bats has long been 
a source of economic loss and hardship for 
cattlemen of Latin America. The transmission of 
paralytic rabies and possibly other diseases, blood 
loss, myiasis, and reduced production of milk 
contribute to a multimillion-dollar problem. 

A research program aimed at developing 
methods for controlling vampire bats began in June 
1 968. It was funded by the Agency for International 
Development (AID), Department of State, under a 
Participating Agency Service Agreement with the 
U.S. Fish and Wildlife Service. Laboratory 
investigations were carried out in Denver, and 
other laboratory and field work took place at the 
Service's Vampire Bat Research Station in Mexico 
City, Mexico. This station officially closed in 
December 1973 after two safe, effective, and 
economical methods of control were developed, 
and research had shifted to observation of their use. 
The control techniques developed use the 
anticoagulant diphenadione and can be referred to 
as the "topical" and "systemic" methods. The 
topical method involves the capturing of vampire 
bats with mist nets set around corralled cattle or at 
cave entrances. Approximately 1.5 cc of a vaseline- 
diphenadione mixture is smeared on the dorsal 
surface of each captured vampire and the treated 
bats are then released. They return to their roost 
and, because they live in compact colonies, 
physically pass the toxicant from one to another. 
Lethal quantities are ingested while grooming. The 
systemic method involves the injection of a solution 
of diphenadione into the rumen compartment of 

cattle. The diphenadione is absorbed into the 
bloodstream of the host and is later ingested in 
lethal quantities by the vampires that feed on blood 
from the cattle. There is no danger to adult cattle 
treated at the recommended levels. The techniques 
are about equal in effectiveness and can usually 
provide 90-95% reduction in parasitism as 
determined by examining the cattle for fresh bites. 

Since 1974 AID has continued to fund the 
program, with the objective of having biologists 
from the Denver Wildlife Research Center help 
Latin American countries develop and initiate 
control campaigns. They could also study special 
problems associated with application of the 
techniques. Nicaragua has been the most aggressive 
country in putting these tools to use. In 1974 the 
Ministry of Agriculture initiated a national 
campaign for control of vampire bats. Statistics 
tabulated for the first 3 years of this program are 
impressive; a total of 240,461 cattle were examined 
and found to have 1 14,629 fresh vampire bites. The 
systemic method was used to treat 1 34,692 cattle, 
and 2,338 vampires were treated with the topical 
technique. The overall reduction in vampire 
parasitism for the 3-year period was 90.7%. 

In June of 1976, the Nicaraguan Ministry of 
Agriculture sponsored the First International 
Symposium on the Control of Vampire Bats and 
Problems Associated with Paralytic Rabies. They 
stated that in 1975 there was not a single case of 
paralytic rabies reported from areas where control 
methods had been applied. They believe that 
paralytic rabies is being eliminated in Nicaragua. 

Vampire Bats and Bovine Milk Production. — 
Parasitism by vampire bats has been alleged to have 
serious adverse effects on livestock health and milk 
production in Latin America, even where rabies is 
not present. To explore this question, milk 
production and blood indicators were measured in 
58 Holstein cows from a dairy herd near Quito, 
Ecuador, and 28 mixed-breed cows from a dairy 
herd near Managua, Nicaragua, before and after 
parasitism by vampire bats (averaging two to four 
fresh bites per cow per night) was reduced 97-100% 
by systemic treatment. In Ecuador the climate was 
mild, the cows were well managed and healthy, and 
milk production was high before treatment; in 
Nicaragua the opposite was true. After treatment, 
blood packed-cell volumes increased significantly 
(P < 0.05) in both herds but milk production and 
hemaglobin counts increased significantly only in 
the Nicaraguan cows. These findings indicate that 
moderately severe parasitism by vampire bats has 
little or no influence on the milk production of 

Vampire bats (Desmodus rotundus) transmit paralytic 
rabies to cattle throughout much of Latin America, 
resulting in thousands of cattle deaths each year. Lowered 
milk production, hide damage, and infected wounds, 
combined with rabies deaths, make this species a serious 
pest of livestock. U.S. Fish and Wildlife Service photo. 

Vampires lap blood from small bites, most commonly 
made around the feet or legs of cattle. U.S. Fish and 
Wildlife Service photo. 

A cooperative project between the Denver Wildlife 
Research Center and the U.S. Agency for International 
Development led to development of an injectable 
anticoagulant formulation which has proven to be an 
effective, low-cost method of controlling bat predation. 
U.S. Fish and Wildlife Service photo. 

otherwise healthy cows in a mild climate but is 
detrimental to health and milk production in cows 
already under stress from poor diet, devitalizing 
climate, and diverse parasites. Thus, where rabies is 
not a factor, the economic benefits of vampire bat 
control may be only marginal for healthy, 
well-managed cows but of definite value for 
low-producing, poorly managed cows in tropical 
environments. This research was funded by the 
Department of State, Agency for International 

Young Calves Susceptible to Diphenadione. — 

The systemic method for controlling parasitism on 
Latin American cattle by vampire bats involves the 
injection of the anticoagulant diphenadione into 
the rumen compartment of the bovine stomach. 
Diphenadione is absorbed into the bloodstream of 
the host and is later ingested in lethal quantities by 
the bats as they feed on blood from the cattle. The 
procedure has been shown to be highly effective and 
safe when used on adult cattle. However, 
laboratory and field data indicated that some 


hazard may be involved when it is used on very 
young calves. Young suckling calves were treated 
by this method and the effects monitored to 
determine if, in fact, they are more susceptible to 
diphenadione poisoning than adult cattle. In 
addition, a possible antidotal procedure was 
examined as well as the effect on toxicity to bats of 
blood from animals treated with the antidotal 
compound. This research was funded by the 
Department of State, Agency for International 

Evidence accumulated to date shows that (1) 
young calves, lacking a fully functional rumen and 
primarily dependent on milk for sustenance, are 
much more susceptible to diphenadione poisoning 
than adult cattle; (2) single intramuscular injections 
of Vitamin K3 given at the time of treatment with 
diphenadione did not offer complete protection 
against diphenadione poisoning in young calves; 
and (3) blood from calves treated with diphenadione 
and Vitamin K3 is as toxic to vampire bats as that 
from animals treated only with diphenadione. 
These results indicate a high degree of risk in using 
the systemic method of vampire control on young 
calves, and the use of the procedure on calves less 
than 4 months old is discouraged. 

Crop Protection by Nonlethal Electric Barrier. 
— Research in the Philippines funded by the 
Agency for International Development, Department 
of State, includes development and experimental 
application of nonlethal electric barriers to protect 
crops from rat depredations. For example, where 
dry-season planting of crops is practiced on 
irrigated land, rats from neighboring areas move 
into the plantings for food and shelter. Barriers 
would have the advantages of permanence and low 
labor costs in these situations. In addition, such 
barriers could be used for isolation of croplands 
from areas where rat densities are high, such as 
marshes and coconut groves, and for protection of 
small plantings of high-value crops. 

A small-scale field test of a nonlethal electric 
barrier produced limited but highly encouraging re- 
sults. The study area in the Philippines consisted of 
four 0.5-acre plots each planted with 10-week-old 
rice. Two plots were fenced with a nonlethal barrier 
charged electrically with a commercial livestock 
shocker; the other two plots were left unfenced in 
order to estimate normal damage to the crop. The 
fence was 14 inches high and constructed with 
bamboo stakes and 0.5-inch-mesh chicken wire. 
Two electrically charged wires and two ground 
wires, spaced 6 inches apart, were fastened with 
insulators to the bamboo stakes. 

Ricefield rat attempting to climb a nonlethal electrical 
barrier in order to feed from a small container of rice. 
Detailed behavioral analyses of the rat-climbing activity is 
monitored through a closed-circuit television camera in 
the foreground. A 95% level of crop protection was 
observed with this barrier design in a field test in the 
Philippines. Photo by J. Stanfield, National Geographic 

Estimates of crop damage, conducted about 2 
weeks before harvest, showed less than 1% of the 
stems cut by rats on the two fenced areas as opposed 
to over 13% on the unfenced areas. These data show 
a 95% level of crop protection with the prototype 
barrier design. 

Laboratory work is progressing to substitute less 
costly materials for barrier construction. A field 
test of the prototype design, on a larger scale, is also 
now under way at the International Rice Research 
Institute in the Philippines. 


Fox Squirrels Repelled by Methiocarb-treated 
Corn Seed. — Methiocarb repellency to fox 
squirrels was tested to determine the primary 
hazard of methiocarb-treated corn seed to this 
species. Ten captive fox squirrels were offered 
several choices of untreated and treated food. 
Squirrels consumed significantly less untreated dog 
food than untreated corn seed (P < 0.01), less 
treated corn than untreated corn (P- <0.01), and less 
treated corn than untreated dog food (P-<0.01). All 
squirrels survived an 18-day period during which 
only methiocarb-treated corn was offered; mean 
weight loss (127 g) during this period was 
significant (P-<0.01). 

Methiocarb's repellency to the test squirrels and 
the survival of the squirrels after prolonged feeding 
on only methiocarb-treated corn indicate that the 
use of this treatment on corn seed poses little, if any, 
immediate hazard to fox squirrels. However, 
potential long-term effects, especially on reproduction, 
require further investigation to confirm safety. The 
results also suggest that methiocarb may have 
potential as a mammal repellent. 

Methiocarb Protects California and Washington 
Sweet Cherry Orchards from Bird Damage. — 
From April through June 1976, methiocarb, a 
bird-repellent insecticide, was tested to determine its 
effectiveness in reducing bird damage to ripening 
sweet cherries in California and Washington. In 
each state, 12 orchards ranging in size from 1.5 to 
6.0 acres, with early maturing varieties and high 
probabilities of bird damage, were selected for 
testing. Six of the 12 orchards were sprayed with 2.0 
pounds (active ingredient) methiocarb in 200-250 
gallons of water per acre from 10 to 14 days before 
the anticipated start of harvest, and 6 were left 

Before the onset of bird damage (12-20 days 
before harvest), 40 trees were randomly selected in 
each orchard, and 50 outermost cherries on one 
randomly chosen branch were marked in each tree. 
Just before harvest, the numbers of bird-damaged, 
missing, and undamaged cherries were counted on 
these samples. 

Methiocarb provided protection from bird 
damage in each state. In California, untreated 
orchards received about 3.2 times the damage of 
treated orchards (3.77% vs. 1.18%), and in 
Washington untreated orchards had 7.5 times as 
much damage (3.28% vs. 0.43%). 

Bird counts supported the damage findings. 
Untreated orchards had about twice as many birds 
as treated orchards in California and about three 
times as many in Washington. In descending order 


, v jWW' 

**- *- 


A mist blower applies methiocarb to sweet cherries in a 
bird-repellent trial in California. Prjofo by O. E. Bray. 

of abundance, robins, waxwings, and house finches 
were most common in California and house 
finches, robins, and starlings in Washington. 

These results should enable the manufacturer to 
obtain a bird repellency label for methiocarb to 
combine with the insecticide registration for sweet 
cherries. This label would be the first granted to a 
chemical for protection of fruit from bird damage. 

Methiocarb Remembered by Redwings. — 
Redwinged blackbirds can remember the repellent 
qualities of methiocarb for periods up to 16 weeks 
after initial exposure. Laboratory tests at the 
Pennsylvania Field Station have indicated that 
after learning an aversion to methiocarb, the 
repellent response, measured by the amount of time 
spent feeding in a 5-minute exposure, is undiminished 
up to 4 weeks after learning and is still strong at 16 
weeks. Other data on the characteristics of redwing 
responses to methiocarb indicate that this species 
forms an aversion to the taste of methiocarb rather 
than to the food base. This finding is in contrast to 
some published data indicating that laboratory and 
wild Norway rats often form aversions to the food 
in which the aversive agent is presented rather than 
to the agent. The redwing data are needed so that 
the potential use of methiocarb as a protectant for 
agricultural crops may be properly assessed. 

Avitrol Registered for Sweet Corn and Sun- 
flowers. — On the basis of data from studies 
conducted in 1974, federal registration for the use 
of 4-aminopyridine formulation, Avitrol FC Corn 
Chops-99S, in field corn was amended in August 
1975 to include sweet corn grown in some regions. 
Registration does not include the States of New 
York, Pennsylvania, West Virginia, Kentucky, 
Tennessee, Arkansas, and Louisiana because 
adequate data on effectiveness of Avitrol were not 


available for these northeastern and southeastern 
areas of the United States. In August 1 976, a similar 
formulation, Avitrol FC Corn Chops-99S, was 
federally registered for protection of ripening 
sunflowers from starlings and certain blackbirds in 
North Dakota, South Dakota, Nebraska, Kansas, 
Oklahoma, Texas, Minnesota, Iowa, Missouri, 
Wisconsin, Ohio, Illinois, Michigan, and Indiana. 
These products of Avitrol Corporation are for use 
by or under the supervision of government agencies 
trained in bird control; they are not for sale to the 

Methiocarb Fails to Protect Michigan Sour 
Cherry Orchards from Bird Damage. — In 1976 
randomly selected halves of eight tart cherry 
orchards in Michigan were either treated with 2.0% 
(active ingredient) methiocarb at approximately 14 
and 7 days before harvest or were left untreated as 
controls. Estimated damage in treated and 
untreated halves did not differ significantly. In the 
orchard with the most bird damage, as measured by 
missing cherries and bird-pecked cherries, damage 
was 40% greater in the treated half than in the 
control half (20.5% vs. 14.5%). For all eight 
orchards, damage in the treated units and the 
untreated units each averaged 5.6%. 

Intensive observations of birds indicated more 
bird activity in the treated than the untreated plots. 
Twelve species were observed feeding on cherries, 
with robins and starlings the most common. 

Because of several factors, including slight 
precipitation after spraying, the presence of birds in 
the orchards, and the fact that damage did occur, 
we believe that this investigation was an adequate 
test of methiocarb. We conclude that methiocarb 
cannot be considered an effective bird repellent for 
sour cherries. 

Registered Avitrol Treatment for Sweet Corn 
May Need Formulation Refinement. — Experi- 
mental Avitrol treatments applied to fields of sweet 
corn in Ohio, Maryland, and New York in 1974 did 
not reduce damage by blackbirds. The bait, cracked 
corn with 1% of the corn particles treated with 
4-aminopyridine, was applied aerially at the rate of 
1 lb /acre, usually every 4 days, to selected fields that 
were within 12 days of their projected harvest. All 
application restrictions specified in the registration 
label for use on field corn were followed. The lack 
of success of the Avitrol treatment in the three tests 
was presumably due, at least in part, to the lower 
blackbird population densities and the low number 
of reacting birds at the experimental sites. 

A review of the factors involved in Avitrol 
cracked-corn treatments suggests that the best way 

to make the treatments effective is to increase the 
proportion of treated corn particles (i.e., a change 
in product formulation). A change in the rate of 
application (1 lb/ acre) seems less desirable because 
chances for ingestion of a treated particle during 
any episode of small-flock feeding would not be 
increased substantially by an increase in application 
rate. Higher rates of treatment of either type, 
however, might substantially increase the kill of 
nonblackbird species. Further evaluations are 
needed to solve this problem. 

Census of Blackbirds and Starlings in Winter 
Roosts in the United States, 1974-1975. — The 
sixth national survey of blackbird-starling roosts 
was conducted by the Fish and Wildlife Service 
during the winter of 1974-75. Most of the data 
collection was through Regional Offices. Cooperating 
ornithology students, whose participation was 
solicited through the National Audubon Society, 
increased survey coverage. The data collected were 
analyzed at the Patuxent and Denver Wildlife 
Research Centers. Data from the East and West 
were combined in an 81 -page report in 1976. 

In all, 723 roosts with an estimated 537 million 
blackbirds and starlings were reported in the 
United States. In the East, 358 roosts with 398 
million birds (74% of the national population) were 
found; in the West, 365 roosts and 139 million birds 
(26%) were reported. The national population was 
composed of 11 species: red-winged blackbirds 
(38%); common grackles (22%); starlings (20%); 
brown-headed cowbirds (18%); Brewer's blackbirds 
(2%); the remainder (trace) included rusty 
blackbirds, boat-tailed grackles, great-tailed 
grackles, tricolored blackbirds, yellow-headed 
blackbirds, and bronzed cowbirds. 

Most roosts in the East were in hardwood 
thickets (41%) or coniferous stands (34%); others 
were in cane, marshes, man-made structures, or 
street trees. In the West, about half of all roosts 
were in marsh habitats and most others were in 
various types of woody vegetation. Field work in 
intervening years between the 1969-70 and 1974-75 
surveys indicated that 25-50 roosts, each of a 
million or more birds, were unreported. 

Most Banded Blackbirds and Starlings Recov- 
ered at Spring Roosts in Ohio Were Banded Near 
Roosts. — After wetting agent treatments at three 
early-spring roosts in central Ohio, 219 banded 
redwings, grackles, cowbirds, and starlings were 
recovered. Of these, 154 (70%) had been banded at 
various times during the year within 100 miles of 
one or another of the roost sites. The recovery of 
such a large proportion of birds within 100 miles of 


A nesting male red-winged blackbird about to enter a de- 
coy trap and acquire a band and leg streamer. Photo by 
O. E. Bray. 

their roosts indicates that many of the roost 
occupants are probably in northern Ohio during 
the period when crop depredations occur and may 
be those most responsible for the damage there. 
Other birds were migrating through central Ohio en 
route to breeding grounds in more northerly latitudes, 
as indicated by the recovery of 59 (27%), all spring- 
summer-, and fall-banded birds that had been 
banded at locations 100-300 miles away in western 
New York, southwestern Ontario, southeastern 
Michigan, and the northern corners of Ohio. Six 
(3%) winter-banded birds had been banded 400-600 
miles to the southwest (in Alabama or Tennessee). 
Some evidence was found for use of traditional sites 
along the north-south migratory pathway and for 
flock tenacity. 

Songbirds Commonly Damage Sunflowers in 
Ohio. — In 1974, about 40% of the birds feeding in 
nine commercial sunflower fields in Sandusky 
County, Ohio, were songbirds (e.g., goldfinches, 
sparrows, and cardinals) and doves. The remaining 
birds were either blackbirds or house sparrows. 
Estimated bird damage in these fields averaged 
3.6% (range 0.7-10.0). These observations suggest 
that certain songbirds commonly use and feed in 
commercial sunflower fields in northern Ohio, and 
therefore any proposed technique for reducing 
blackbird damage to these fields in Ohio should be 
carefully tested for hazards to nonblackbird species. 

Bird Hazard to Aviation Increasing. — Many 
bird/plane strikes, 1973 through 1975, resulted in 
engine ingestion of birds, causing serious damage 

and loss of aircraft and human life. Executive jet 
engines appear very vulnerable to bird damage. 
Five of these aircraft have been lost due to engine 
ingestion of birds — Lear Jets at Atlanta, Georgia 
(cowbirds) and Watertown, South Dakota (gulls); 
and an HS-125 at Downsfold, England (lapwings). 
All passengers were killed in the Atlanta accident, 
occupants were injured at Watertown, and six 
people in a car were killed when struck by the HS- 
125. Many serious bird/ plane strikes involving 
commercial aircraft have occurred throughout the 
world; the wide-bodied jets, particularly the 747 
and the DC- 10, appear as vulnerable as older 
aircraft. Most of the serious strikes occurred during 
takeoff, a most hazardous situation because many 
of these aircraft were heavily loaded international 
departures. Many serious strikes have involved 
gulls, species that are an increasing worldwide 
hazard. Known techniques for keeping runways 
and airport areas free of gulls (and other birds) are 
apparently not being routinely and responsibly 
applied, and the record indicates that extreme bird 
hazards are present. The recent loss of a DC- 10 on 
takeoff at JFK Airport is an example of these 

The present critical need of both civil and 
military aviation in the United States is a systematic 
program to bring about responsible and continued 
use of known remedial measures. The record of 
incidents and losses indicates that highest priority 
should be given to effecting measures for repelling 
birds — particularly gulls, blackbirds, and starlings 
— from airports, especially from runways and 
adjacent areas. In addition, military low-level missions 
should not be flown in areas of high bird hazard. 

Starlings Only Threat to Winter Wheat in 
Tennessee. — Starlings inflicted 100% of the 
damage to sprouting winter wheat in the winter of 
1975-76 in Gibson County, Tennessee, where an 11- 
million-bird blackbird/ starling roost was located. 
Wheat made up 41% of the food items in starlings 
collected in November, in contrast to 0% for 
grackles, red-winged blackbirds, and brown- 
headed cowbirds. A survey of 48 randomly selected 
wheat fields in the foraging area of the roosting 
birds revealed that 31% of the fields had been 
damaged by starlings (i.e., pulling out emerging 
sprouts). Overall, an estimated 3.5% of the wheat 
sprouts were removed from the 48 fields. The best 
way to reduce or eliminate damage is to plant fields 
by early November. The 33 fields planted before 
November 13 sustained no bird damage, but all 15 
fields planted on that date or later received some 


Differences Between Bird and Mammal Toxi- 
cation Systems. — Microsomal mixed-function 
oxidative enzymes in the livers of animals play 
important roles in the toxication and detoxication 
of foreign compounds. These hepatic enzymes or 
enzyme systems are being studied as a means of 
developing chemicals that will selectively alter the 
physiology or behavior of depredating animals. In 
recent studies, p-chloroaniline was found to be a 
good model in the comparative study of the N- 
hydroxylation (a toxication process) of primary 
aromatic amines by male red-winged blackbirds 
and albino rats. Various reaction parameters were 

investigated. Under optimum reaction conditions, 
the ,/V-hydroxylation activities of redwing hepatic 
microsomes were about 2.5 times lower than those 
of analogous preparations from rat livers. The 
microsomal protein and cytochrome P-450 
concentrations of the hepatic microsomes of both 
species were also found to differ. Both concentrations 
had significantly smaller values in birds than in rats. 
Exploitation of these and other basic avian- 
mammalian differences could lead to control 
methods that would affect only the target animal — 
and not other animals or the environment. 

Environmental Contaminant Evaluation 


Acute Toxicity of Chemicals. — Capabilities of 
the Fish-Pesticide Research Laboratory and its 
field stations for research on acute toxicity were 
integrated to meet the needs for two major data 
bases. The most urgent need for such data related to 
the Fish and Wildlife Service's concern that massive 
spraying operations for spruce budworm control in 
the northeastern United States may adversely affect 
the restoration of Atlantic salmon, as well as 
damage other aquatic resources. Technical and 
field formulations of several registered and 
experimental insecticides were investigated in these 
studies. The U.S. Forest Service provided sufficient 
field data and information on anticipated use 
patterns to enable us to design research applicable 
to appropriate species and water types representative 
of the areas to be treated. Results of the work were 
used by the Regional Office, Boston, Massachusetts, 
in modifications of overall spraying operations to 
reduce the effects of the insecticides on aquatic 

The second major effort of this section involved 
testing several technical and field formulations of 
herbicides. Special emphasis was placed on 
glyphosate, which appears environmentally safe 
and effective for vegetation management. Results 
of the research on herbicides and forest insecticides 

are summarized in later sections of this report. 

Other chemicals tested for acute toxicity 
included manufacturing contaminants of penta- 
chlorophenol and three water-soluble fractions of 
crude oil. Accidental spills of pentachlorophenol, 
which is commonly used as a wood preservative, 
have caused fish mortalities in Missouri and 
elsewhere. However, this compound also contains 
dioxins and dioxin precursors (predioxins) which 
exist at concentrations up to 0.1%. Dr. C. Rappe, 
University of Umea, Sweden, who has synthesized 
three predioxins, has provided us with small 
amounts of these chemicals for preliminary toxicity 
tests. The 96-hour LC50'sfor all three predioxins to 
scuds, midge larvae, and fathead minnows were 
greater than 0.5 mg/1. Longer tests will be required 
to determine whether these impurities contribute 
significantly to the toxicity of pentachlorophenol. 
Studies of the toxicities of three water-soluble 
fractions of crude oil — toluene, benzene, and ethyl 
benzene — to bluegills yielded 96-hour lC50'sof 1 
to 50 mg/1. 

Overall, 30 chemicals were tested for their acute 
toxicity to fish and aquatic invertebrates. The data 
generated were more definitive than those from 
past acute toxicity studies in that a greater number 
of species were tested in a variety of waters 
simulating different biogeographical areas. The 
results of these tests also indicated that 16 of the 30 
chemicals should be considered for more detailed 


research. Personnel in the section responded to 
more than 100 requests from chemical industries, 
Federal and State agencies, and other researchers 
for acute toxicity data. 

Orthene Appears Safest of Proposed Forest 
Insecticides. — The Fish-Pesticide Research 
Laboratory continued research support of both the 
Fish and Wildlife Service's Atlantic salmon 
restoration program and the Forest Service's forest 
insect control programs by estimating the relative 
environmental acceptability of candidate insecticides. 
In 1975 and 1976, the Forest Service sprayed more 
than 5.5 million acres in Maine and Montana to 
control the spruce budworm. The areas sprayed 
involve divergent biogeographical regions with 
various water qualities and associated aquatic 
organisms. In 1976, Dylox, Matacil, Orthene, 
Sevin, Sumithion, and Lannate were tested against 
species characteristic of cold-, cool-, and warm- 
water habitats, and in water types characteristic of 
the areas to be sprayed. 

All of the insecticides tested were many times 
more toxic to aquatic invertebrates than to fish. 
The 96-hour LC50's of technical grade Dylox, 
Matacil, Sevin, and Sumithion ranged from 3 to 
40 jzg/ 1 for scuds, stonefly naiads, and midge larvae, 
and from 1,600 to 3,900 /ig/1 for cutthroat trout, 
brook trout, bluegills, and yellow perch. In 
contrast, the toxicity of Orthene was about 10,000 
ug/1 to invertebrates and over 100,000 jug/1 to fish. 
The field formulation of Matacil was about 70 
times more toxic to fish than its technical form, and 
the difference was apparently due to some additive 
in the formulation. Toxicities of the six insecticides 
tested were altered in waters of different temperature, 
hardness, or pH. For example, the toxicities of 
Dylox, Matacil, and Sevin to fish were 4 to 21 times 
greater in water of pH 8.5 than in water of pH 7.5. 
Therefore these chemicals could pose a greater 
hazard to aquatic organisms in Montana (where 
stream pH is commonly 8.5 to 8.8) than in Maine 
(where pH is lower). In rainbow trout and channel 
catfish, eggs were relatively more resistant to all of 
the insecticides than were swim-up fry and fingerlings. 

Field studies by the Forest Service show that 
water collected 30 and 120 minutes after an aerial 
application of Dylox in 1975 contained residues of 
260 and 7 /zg/1, respectively. If such residues in 
water are representative of what might also be 
expected for Orthene, Sevin, Sumithion, and 
Lannate, these insecticides should not cause 
significant fish mortalities. However, comparable 
residues of the field formulation of Matacil could 
kill fish. All of the insecticides tested, except 

Orthene, may cause significant mortalities of 
stream invertebrates and affect fish populations 
indirectly by reducing their food. Overall, our acute 
toxicity studies suggest that the field formulation of 
Matacil is the least, and Orthene the most, 
environmentally acceptable of the six chemicals 
tested for spraying near aquatic habitats. 

Experimental Insect Growth Regulator Tested 
Against Aquatic Organisms. — Dimilin (TH 60-40) 
is an insect growth regulator that inhibits 
maturation of juvenile insects. It is among a group 
of new compounds that have been proposed as 
being environmentally safer than the more 
conventional insecticides. Insect growth regulators, 
which are not supposed to be directly toxic to target 
insects, produce structural changes during insect 
development that indirectly cause mortality. 
Dimilin shows high biological activity against a 
variety of target pest insects, and experimental 
permits for its use on gypsy moth, spruce budworm, 
cotton boll weevil, and mosquitoes have been 
granted by the Environmental Protection Agency. 

Because Dimilin may be used extensively in or 
near aquatic habitats, we determined its toxicity to 
invertebrates and fishes inhabiting cold and warm 
waters. Because of the unique mode of action of this 
compound in inhibiting metamorphosis of 
immature insects, we were not surprised to find it 
relatively nontoxic to fish. The acute, static 96-hour 
LC50's were greater than 100 mg/1 for rainbow 
trout, fathead minnows, channel catfish, and 
bluegills. However, crustaceans such as daphnids 
and scuds were highly sensitive to Dimilin; 48-hour 
EC 50's ranged from 1 5 to 45 jug/ 1. In contrast, midge 
larvae were less sensitive than crustaceans (48-hour 
EC 50's, 560 /ig/1), but chronic exposures showed 
that emergence of adult midges was reduced 25% by 
a concentration of only 6 jug/1. 

Three degradation products of Dimilin were also 
tested for their acute toxicity. The most toxic of the 
three was 4-chloroaniline; the 48-hour EC 50 was 
43 mg/ 1 for midge larvae and the 96-hour LC 50 was 
2.4 mg/1 for bluegills. Comparable values for 4- 
chlorophenyl urea and 2,6-diflurobenzoic acid 
exceeded 1 00 mg/ 1 for midge larvae, rainbow trout, 
channel catfish, and bluegills. 

Based on the maximum recommended application 
rate of 0.16 pound of Dimilin to 1 acre-foot of water 
(0.06 mg/1) for mosquito control, no acute adverse 
effects on fish would be expected, but populations 
of important fish food organisms, such as Crustacea 
and midges, could be reduced. 

Research on Herbicides. — Herbicides are used 
extensively by Federal agencies to manage 


vegetation on public lands and in or along 
irrigation and reservoir systems. Such chemicals 
may enter aquatic habitats by intentional direct 
application to water or by unintentional drift and 
runoff from adjacent land. For example, in 1975 the 
U.S. Bureau of Reclamation used over 1.5 million 
pounds of herbicides to control vegetation 
associated with western irrigation systems, and the 
Fish and Wildlife Service applied 340,000 pounds 
on refuge lands and fish production facilities. 
Several ester formulations of 2,4-D are used by the 
Forest Service to stimulate grass production 
through sagebrush control. Earlier, we found that 
the butyl ester (BE) and the propylene glycol butyl 
ether ester (PGBEE) of 2,4-D were toxic to lake 
trout at concentrations of about 1,000 jug/ 1, and 
that longer exposures to concentrations down to 
33 jug/1 adversely affected young trout. In 1976, we 
conducted similar tests with cutthroat trout 
because they are more closely associated with 
streams in the sprayed areas than lake trout, and 
some strains of cutthroat trout are on the 
endangered species list. Toxic concentrations for 
cutthroat trout were in the range of 320 to 350 jug/ 1, 
but exposure to a single application of 100jug/l had 
no effect on fry or fingerlings. However, continuous 
exposures of the young to concentrations of 20 to 
30 jug/1 reduced growth and survival. Field 
investigations by the Forest Service show that 
residues of 2,4-D BE or 2,4-D PGBEE may reach 
1,000 jug/1 in streams after spraying and persist at 
lower concentrations for about 10 days. Because 
such concentrations pose a significant hazard to 
fisheries, our results were submitted directly to the 
Forest Service for consideration in future 
sagebrush control procedures. 

Simazine and 2,4-D DMA are now registered by 
the Environmental Protection Agency (EPA) for 
certain aquatic weed problems associated with 
navigation, irrigation, and management of fishery 
habitats. These registrations were contingent on 
our residue and toxicological investigations over 
the past 3 years. Chronic toxicity studies in 1976 
were designed to detect sublethal effects of the two 
chemicals under contrasting conditions of continuous 
exposure and exposures simulating actual use. 
Under the latter condition, Simazine had no 
adverse effect on survival, growth, or reproductive 
success of fathead minnows, but continuous 
exposure to 2,500 jug/1 caused a 12% decrease in 
growth in fry. The 2,4-D DMA appeared to have no 
serious adverse effects on fathead minnows, but 
growth of young fish was stimulated by both 
continuous and use-pattern exposures. 

In 1975, we found that some chemicals used to 
control plant growth in irrigation systems might 
influence distribution of fish in streams that receive 
irrigation return flows. Rainbow trout fry avoided 
sublethal concentrations of copper sulfate or xylene 
down to 0.1 /ig/1 and 100jug/l, respectively. They 
did not avoid acrolein before receiving a lethal 
exposure. We conducted similar studies in 1976 
with mayfly nymphs and tested copper sulfate, 
xylene, acrolein, diquat, dalapon, Aquathol K, 
2,4-D DMA, and Roundup. The nymphs did not 
avoid any of these chemicals at concentrations that 
might occur in irrigation return flows following 
weed-control applications at recommended rates. 
One of the herbicides tested in the avoidance 
studies, Roundup, was also investigated for its 
toxicity to fish and aquatic invertebrates because it 
is relatively new and appears particularly effective 
for control of emergent vegetation along irrigation 
ditch banks, or on refuges and fish hatcheries. It is 
being developed for various broad agronomic uses 
because it is relatively nontoxic to animals, 
immobile in soils, and appears highly degradable. 
The results showed that the active ingredient, 
glyphosate, was much less toxic to fish and 
invertebrates than the Roundup formulation. The 
96-hour LC50 for Roundup to fathead minnows 
was 2.3 mg/1, whereas the LC50 for glyphosate to 
rainbow trout was 140 mg/1. The toxicity of the 
surfactant used in the formulated product was 
similar to that for the whole formulation. Also, the 
toxicity of Roundup in water was not reduced after 
aging for 7 days, probably due to stability of the 
surfactant. Sac fry and early swim-up fry of 
rainbow trout were more sensitive to glyphosate 
and Roundup than were the eggs. These results 
suggest that a change in the formulation of 
glyphosate would greatly improve its environmental 

2,4-D DMA Influences Pond Community 
Interrelations. — Research was begun in the 
summer of 1975 to identify major limnological 
characteristics of ponds that are most useful in 
monitoring and predicting impacts of contaminants 
on aquatic communities. Of 12 ponds used in the 
study, 4 were treated with 1 mg/1 and 4 with 2 mg/1 
of 2,4-D DMA, and 4 were untreated. Twenty 
measurements of physical, chemical, and biological 
characteristics of the ponds were incorporated into 
a descriptive statistical model of related variables. 
Both concentrations of 2,4-D DMA suppressed the 
growth of occasional arrowhead plants {Sagittaria 
montevidensis) for about 6 weeks, but common 
waternymph (Najas guadalupensis) and stonewort 


(Chara spp.), which together nearly covered the 
bottoms of the experimental ponds, were not 
reduced by even the high concentration. However, 
aerial photographs revealed that 1 mg/1 apparently 
stimulated growth of submerged vegetation. 

Several effects associated with the herbicide 
treatments appeared in nontarget organisms. 
Bluegills in ponds treated with 2 mg/1 of 2,4-D 
DMA grew faster than fish from untreated ponds, 
or ponds treated with 1 mg/1 of 2,4-D DMA. 
Laboratory tests in which phytoplankton was 
collected at intervals from untreated ponds and 
exposed to 2,4-D showed that 2 mg/1 of the 
herbicide significantly increased algal production, 
but 1 mg/1 did not. Although 2 mg/ 1 increased algal 
production experimentally and increased photo- 
synthesis in ponds, it is questionable whether 
increased production was responsible for the entire 
increased growth rate of fish in ponds treated with 
2 mg/1 of 2,4-D DMA. Other laboratory studies 
showed that 2,4-D DMA by itself can also increase 
growth and sexual maturation of fathead minnows. 

Although 2,4-D DMA did not seriously affect 
the major rooted plant species, treatments of 2 mg/1 
influenced pH, turbidity, alkalinity, and conductivity 
and lowered the magnitude of diurnal oxygen 
changes in ponds. Such oxygen changes are good 
estimators of total biological productivity and 
suggest reduced photosynthesis due to a stress on 
the plant communities. This condition would 
probably increase cycling of plant nutrients, such as 
phosphates or nitrates, back into the pond water. 
Therefore, 2,4-D may stimulate algal production 
directly, as in the bioassay experiments, or 
indirectly by releasing more inorganic nutrients. 

Variations in 14 water-quality characteristics 
(such as pH, turbidity, conductivity, and P0 4 ) of 
2,4-D treated and untreated ponds were compared 
by stepwise multiple regression with concentrations 
of chlorophyll a, a measure of the weight of algae in 
water. In this analysis, only the factors which are 
most statistically significant are compared in the 
final computations. Turbidity was significantly 
associated with chlorophyll in the control ponds, 
whereas conductivity replaced turbidity as the 
single most statistically significant variable in 
ponds treated with 1 mg/1 of 2,4-D DMA. In the 
high-treatment ponds, chlorophyll concentration 
was correlated with the inorganic phosphate, 
followed by turbidity and conductivity. Therefore, 
increased algal production in ponds treated with 
2,4-D DMA is probably due to a combination of 
direct stimulation of photosynthetic activity, and 
(indirectly) increased release of macrophyte 

nutrients. These investigations were continued 
during the summer of 1976 with relatively heavy 
treatments of two herbicides, dichlobenil and fenac. 

Benthic Hydrosoil Communities, Geochemical 
Cycling, and Contaminant Impacts. — The 
Nation's waters are one vehicle for the transport 
and distribution of synthetic chemicals and other 
industrial and agricultural wastes. However, 
monitoring of various pollution problems suggests 
that many such contaminants form complex 
associations with organic and inorganic particulate 
materials in water, some of which settle to the 
bottom and are incorporated into sediments. The 
bottom, or benthic, regions of aquatic ecosystems 
provide habitat for numerous invertebrates and 
other important fish and wildlife foods. These 
regions also support a relatively fragile, thin zone of 
microorganisms, usually no more than a few inches 
thick below the water-mud interface, frequently 
termed the hydrosoil. This zone performs a vital 
function in the decomposition of biological matter, 
and in the recycling of inorganic nutrients back into 
production of fish and other essential components 
of aquatic communities. The well-being of all 
aquatic organisms is intimately interwoven with 
microbial activity in the sediments. It is well known 
that benthic microorganisms can modify or 
degrade various synthetic chemicals, but little is 
known about the types of microorganisms present, 
their microenvironmental requirements, or 
whether contaminants in sediments constitute a 
hazard to normal benthic microbial action. 

Over the past year, Laboratory scientists 
modified and adapted about 15 agricultural and 
limnological techniques into a rapid screening test 
that infers impact or nonimpact of chemicals on the 
physiology of microorganisms in natural benthic 
hydrosoils. The test is based on general physiological 
processes that are essential to recycling of carbon, 
nitrogen, sulfur, and phosphorus. Tests of 50 
insecticides, herbicides, and industrial chemicals, 
including such materials as DDT, atrazine, 
Arochlor 1254, 2,4-D DMA, leptophos, hexa- 
chlorobenzene, and toxaphene, for activity against 
benthic microorganisms revealed that more than 
half of these affect the growth of microorganisms. 
More elaborate experiments are under way to 
determine which general physiological processes of 
the hydrosoil communities responsible for cycling 
nutrients are affected by the contaminants. Also, 
we wish to determine whether effects on such 
processes are commensurate with real or expected 
concentrations of the contaminants in sediments, 
the hydrosoil conditions associated with microbial 


inhibition, and the relative sensitivity of benthic 
communities from other geographical regions. We 
believe such tests could become a powerful tool in 
estimating potential effects of new synthetic 
chemicals on cycling of nutrients in aquatic 
ecosystems, in interpreting data from environmental 
monitoring of chemical residues, and in general 
biological monitoring of aquatic ecosystems. 

Modular Food Chain Research Nears Com- 
pletion. — This 2-year investigation funded by the 
Office of Toxic Substances of EPA was undertaken 
to develop a reliable biological model for 
estimating the uptake, transfer, and degradation of 
xenobiotic chemicals in segments of an aquatic 
food chain. Partial results were reported in the 
1974-75 Annual Report. A protocol for the 
modular food chain was published in the Federal 
Register in 1975. The major objectives of the 
research were to test the overall reliability of the 
model and to measure effects of different operating 
conditions on variability of data generated by the 
test system. These objectives have been met, and the 
data will be used in assessing the suitability of the 
model for pretesting of chemicals according to 
requirements of the Toxic Substances Control Act 
of 1976. 

Mayflies Prove Effective in Monitoring PCB's. 
— The Upper Mississippi River provides important 
habitat for sport and commercial fisheries, but 
residue monitoring of fish from some segments of 
the river has revealed extensive pollution by 
polychlorinated biphenyls (PCB's). The burrowing 
mayfly, Hexagenia bilineata, is an important 
natural fish food in the Upper Mississippi River 
and is one of the most abundant aquatic insects in 
the navigation pools. We analyzed adult mayflies to 
better define benthic distribution of PCB's in the 
River because their immature forms (naiads) are 
relatively sedentary bottom dwellers, and the adults 
are abundant and easy to collect. Also, since the life 
cycle of mayflies is normally completed in 1 year, 
residue concentrations represent an annual 
accumulation which can be followed from year to 

Adult mayflies, collected for us by public 
cooperators at 14 stations along 160 miles of the 
Mississippi River, contained PCB residues as high 
as 2.9 Mg/g, based on whole body weight. Residue 
levels were highest in adult mayflies collected from 
the Lake Pepin area, a natural lake on the 
Mississippi River, which is about 60 miles 
downstream from Twin Cities, Minnesota. 
Generally, PCB residues in carp collected from this 
area were four to five times higher than those in 

Mayfly adult (above) and naiad (below) in hydrosoil from 
the upper Mississippi River. Photos by C. Fremling. 

mayflies, probably because of the higher lipid 
content of the carp. The uptake of PCB's by mayfly 
naiads is probably by way of both water and food, 
since they live in burrows, and significant PCB 
residues in streams and rivers are believed to be 
associated with suspended materials and hydrosoils. 
Much of the suspended material in the River settles 
to the bottom as it flows into Lake Pepin and 
current velocity slows. Thus, the lake may become a 
large settling basin for PCB's sorbed to sediments, 


and benthic food-chain elements of the lake may 
accumulate considerable amounts of PCB residues. 

An extensive survey of PCB residues in mayflies 
collected from the entire length of the Mississippi 
River, as well as from some of the major tributaries, 
is under way. Samples are also being collected from 
several pristine lakes in Minnesota and Wisconsin. 

Aroclor 1254 (PCB) Impairs Growth and 
Development of Brook Trout. — Polychlorinated 
biphenyls are now considered a ubiquitous 
pollutant of freshwater ecosystems in the United 
States; residues in fish range from 0.1 to over 150 
/ig/g. Residues of this contaminant in important 
salmonid fishes of the Great Lakes, northeastern 
United States, and elsewhere prompted us to study 
its effect on growth of early life stages of brook 
trout, a widely distributed salmonid. We also 
wished to determine whether subtle, more sensitive 
biochemical measurements could detect adverse 
effects of PCB's. 

Eyed eggs of brook trout were exposed to water 
concentrations of Aroclor 1254 ranging from 0.44 
to 12.6 ug/1. After hatching, the fry were exposed 
for 120 days. Median hatch time, percentage hatch, 
and percentage sac-fry mortality were not affected. 
However, fry mortality increased in the highest 
exposure 7 days after yolk absorption. Mortality 
also increased in fry exposed to the lower 
concentrations, 10 to 80 days after yolk absorption. 

The growth of brook trout fry was significantly 
reduced below that of controls by Aroclor 1254 
concentrations of 1.5/ig/g or higher at 10 days after 
yolk absorption. However, at 1 20 days after hatch, 
growth of the surviving brook trout was similar to 
or greater than that of controls. Biochemical 
observations of backbones in fish exposed for 80 
days showed that collagen levels decreased and 
calcium increased at Aroclor 1254 concentrations 
of 0.71 fxg/g anu greater. This collagen-calicum 
imbalance appears to be indirectly indicative of 
other toxicological disorders, which are discussed 
in the next section of this report, concerning the 
effects of toxaphene. The early developmental 
stages of brook trout were the most sensitive, and 
the initial effects on bone development remained 
evident through the later stages of growth. Fish 
with reduced growth at 10 days post-yolk 
absorption contained residues of 9 to 400 jug/ g. The 
bioaccumulation (40,000 to 49,000 times) of 
Aroclor 1254 by brook trout was similar at all 
concentrations at the end of the study. However, 
during the sac-fry stage, fish in the lowest 
concentration had bioaccumulation factors three 
times greater than those of fish in the highest 


Further work on PCB's will involve the 
determination of the most persistent and toxic 
components. Recent studies with mice have shown 
that the toxicity of PCB's and their storage in fatty 
tissue vary widely with the positions of the chlorine 
atoms on the biphenyl ring. We have separated 
PCB's into subfractions, using activated carbon on 
polyurethane foam. These fractions contain PCB's 
with decreasing chlorine substitution in biphenyl 
o,o'-positions. Tests of the toxicity to fish and fish- 
food organisms of these fractions will provide a 
measure of their respective importance in PCB 
pollution and may permit more meaningful 
analyses of PCB residues. 

Biological Impact of Toxaphene on Aquatic 
Organisms. — Toxaphene is an organochlorine 
insecticide used extensively in the southeastern 
United States for pests on cotton, and residues of 
toxaphene have been reported as high as 48#g/gin 
fish from that area. For the past several years, EPA 
has partially funded our research on toxaphene to 
assist in developing water quality criteria for this 
insecticide. However, the work was also directed 
toward toxicological interpretation of toxaphene 
residues in fish and their significance to fishery 
resources, and toward the development of 
biochemical techniques that may have utility as 
sensitive indicators of pollution-induced stress in 
the field. 

Fish were more sensitive to toxaphene than were 
aquatic invertebrates. The acute toxicity of 
toxaphene to daphids (Daphnia magna), a scud 
(Gammarus pseudolimnaeus), and midge larvae 
(Chironomus plumosus) ranged from 10 to 180 
jug/1, whereas the acute toxicities for brook trout, 
fathead minnows, and channel catfish were 4. 1, 5.3, 
and 15.2 /ig/1, respectively. Among invertebrates, 
daphnids were more susceptible to chronic 
exposures of toxaphene than scuds or midge larvae. 
Under chronic conditions, toxaphene had little 
effect on reproduction of brook trout, fathead 
minnows, and channel catfish; however, growth of 
offspring in each species was significantly 
decreased. In addition to length and weight being 
decreased by toxaphene, backbone development in 
each species was also impaired. Collagen synthesis 
in the backbone was inhibited and resulted in an 
increase in the ratio of minerals to organic matrix. 
As a result, vertebral columns of the fish became 
more brittle and susceptible to being fractured or 
broken. Toxaphene residues in fish from these 
studies were in the range of those reported in fish 
collected in national pesticide residue monitoring 


Effects of 150-day toxaphene exposure and dietary vitamin C concentration on growth and skeletal development in 
channel catfish. A is a fish fed a diet containing 670 mg/kg of vitamin C and not exposed to toxaphene, B is a fish fed a diet 
containing 670 mg/kg of vitamin C and exposed to 475 mg/l of toxaphene, and C is a fish fed a diet containing 63 mg/kg of 
vitamin C and exposed to 37 mg/l of toxaphene. Arrows indicate protrusions of vertebral column. Photo by W. A. 

programs. This relationship suggests that the 
insecticide may have subtle, adverse effects on basic 
biological processes of fish in areas of toxaphene 

In further studies, we determined that nutritional 
factors can influence the tolerance of fish to 
toxaphene. Vitamin C, an essential dietary nutrient 
for fish, is involved in detoxication mechanisms in 
the liver and in collagen formation by hydroxylative 
enzymes. Inasmuch as these two hydroxylation 
processes might compete for vitamin C and cause 
decreased collagen, we attempted to determine the 
effects of toxaphene on the distribution of 
vitamin C in liver and bone in channel catfish fry. 

The fry were exposed to toxaphene (0, 37, 68, 106, 
218, and 475 ng/1) for 150 days. The fish were 
divided into three groups within each concentration, 
and each group was fed a diet with different 
amounts of vitamin C (63, 670, and 5,000 mg/kg). 
All toxaphene concentrations decreased backbone 
collagen in fish fed the low vitamin C diet, and the 
three highest concentrations of toxaphene 
decreased collagen in fish fed the 670 mg/kg diet, 
but only the highest toxaphene concentration 
decreased collagen in fish fed the diet containing 
5,000 mg/kg of vitamin C. The incidence of spinal 
deformities decreased with increased dietary 
vitamin C, as did the effects of toxaphene on 


mucous cells of the skin and gill cartilage. The effect 
of toxaphene on mucous cells could increase the 
susceptibility of fish to diseases, impair wound- 
healing processes, and compromise the ability of 
fish to respond to natural stresses. Our investigations 
indicate that availability of essential nutrients, such 
as vitamin C, in natural food sources must be 
considered when one interprets the biological 
significance of toxaphene residues in fish from a 
given environment. 

Biochemical Indicator of Fish Growth Under 
Development. — Chronic toxicity studies with fish 
are expensive, high-risk endeavors, requiring from 
10 to 12 months to conduct. Such studies include 
growth, reproduction, and survival of adults, and 
growth and survival of the offspring. As a 
consequence, there has been much interest in the 
development of alternative methods that provide 
similar information with less expenditure of time 
and effort. Therefore, we attempted to assess the 
possibility of using biochemical factors as 
indicators or predictors of growth and development 
in fish. Growth of fish is usually evaluated by 
measuring weight and length; however, biochemical 
changes due to toxic materials should, logically, 
occur before becoming evident as a reduction in 
growth. This approach was incorporated into our 
investigations of toxaphene. 

We selected collagen and hydroxyproline 
concentrations in collagen for our studies because 
collagen is the major fibrous protein and 
component of the organic matrix of bone and other 
connective tissues in vertebrates, and functions as a 
structural support for these tissues. Fish continue 
to grow throughout their life and must have proper 
collagen formation to enable their backbone 
vertebrae to increase in size in proportion to 
growth. For normal growth and bone development 
to proceed, vitamin C is needed for collagen 
synthesis because it is an essential cofactor for the 
enzyme collagen hydroxylase. This enzyme 
catalyzes the hydroxylation of proline to hydroxy- 
proline, which is an amino acid that is necessary for 
the structural integrity of the collagen matrix. 
However, if large amounts of the body's supply of 
vitamin C are utilized for the detoxication of a 
chemical, other essential processes that require 
vitamin C, such as collagen formation, may be 
severely restricted. Fish are especially vulnerable to 
such interference from chemical contaminants 
because they cannot synthesize vitamin C and must 
depend upon a finite dietary intake as a source. We 
have found that hydroxyproline and backbone 
collagen concentrations are sensitive biochemical 

indicators of growth in fathead minnows, brook 
trout, and channel catfish exposed to toxaphene. 
Decreases in collagen and hydroxyproline con- 
centrations occurred at least 30 days before changes 
in weight or length were evident. Similar results 
were observed in brook trout exposed to Aroclor 
1254 and in fathead minnows exposed to the 
dimethylamine salt of 2,4-D. Results from these 
studies suggest that collagen and hydroxyproline 
measurements can be used as indicators and 
predictors of growth in fish to shorten chronic 
toxicity tests. Other biochemical processes, such as 
the ability to respond to stress, require vitamin C 
and could also be affected when large amounts of 
vitamin are used by the liver for the detoxication of 
organic contaminants. 

The effect of toxic materials on collagen 
formation is not species specific. Through 
cooperative research with the Patuxent Wildlife 
Research Center, we found that chronic exposure 
of black ducks to toxaphene caused effects similar 
to those observed in fish, i.e., a decrease in both 
growth and backbone collagen. These changes in 
collagen metabolism in birds may also be related to 
the thin eggshell phenomenon, since collagen 
is also the main organic matrix around which 
mineral salts are deposited in the shells of eggs. 

National Fish Monitoring Activities Relocated 
in Columbia. — The Fish and Wildlife Service 
became a participant in the National Pesticide 
Monitoring Program in 1967, with responsibility 
for measuring trends of pesticide residues in fish 
collected from the major watersheds across the 
nation. The program was designed to provide the 
minimum monitoring needed to establish baselines, 
detect residue trends over time, and identify 
potential pollution problems. Fish collections were 
made annually until 1975, when they were 
terminated to enable the Service to evaluate the 
monitoring activities and develop research- 
supported capabilities for chemical analysis of 
samples and interpretation of data. The analytical 
work group is now located at the Fish-Pesticide 
Research Laboratory, Columbia, Missouri, and is 
called the Aquatic Contaminant Monitoring Team. 
The Team will function with research elements of 
the Laboratory, regional environmental con- 
tamination evaluation specialists, and with other 
monitoring activities of the Service coordinated in 
the Washington, D.C., office. Team activities in 
1976 have been limited to planning, staffing, and 
preparing analytical laboratory equipment and 

In 1976 and 1977, the Team will be involved in 


two types of monitoring activities. The first 
approach is traditional and is designed to detect 
trends in contaminant residues in fish. Fifty of 100 
designated stations divided among 12 major 
drainage systems in the United States will be 
sampled in alternate years. Three composite 
samples will be taken from each station for analysis 
of whole-body residues of heavy metals and organic 
chemical contaminants. Objectives of this approach 
are to distinguish general trends in use patterns and 
disposal of environmental contaminants, and to 
estimate their distribution in freshwater fisheries 
over an extended period of time. The samplings are 
useful in reflecting the impact of regulatory actions 
on selected chemicals, as well as providing 
laboratory scientists an opportunity to analyze the 
collections for new contaminants. 

The second approach is designed to provide 
special, short-range investigative capabilities which 
are coordinated with the regional offices, the Fish- 
Pesticide Research Laboratory, and the Washington, 
D.C., office. Investigative monitoring will focus on 
local or regional contaminant problems and will 
require more intensive effort than can be provided by 
monitoring of trends. Three investigative monitoring 
projects have been carried through the planning 
phases, and collections have been partially 
completed for 1976. One such study concerns the 
impact of environmental contaminants on striped 
bass along the Atlantic coast. This study is an effort 
to determine the influence of organochlorine, PCB, 
and heavy metal residues on survival and 
development of striped bass progeny through the 
eighth day of development. Two other investigative 
monitoring projects are under way to (1) determine 
point sources of unexpectedly high DDT con- 
tamination along the Rio Grande in Texas, and (2) 
analyze lake trout from Lake Michigan to ascertain 
the extent of toxaphene and PCB contamination. 
These investigations should be nearing completion 
in the summer of 1977. 

Dioxin Removal from "Herbicide Orange" 
Proved Feasible. — Last year, chemists at the Fish- 
Pesticide Research Laboratory discovered a 
purification process which may permit reclamation 
and domestic use of millions of dollars worth of 
"Herbicide Orange" which is now impounded by 
the United States Air Force. This herbicide cannot 
be used domestically because it was found to be 
heavily contaminated with dioxins. Chlorinated 
dioxins and related dibenzofurans are among the 
most toxic compounds known to man, yet they 
have been found in widely used chemicals, such as 
the wood preservative pentachlorophenol and 

formulations of the herbicide 2,4,5-T. Even with 
present technology, trace amounts of dioxins are 
unavoidably formed during the manufacture of 
several of these types of chemicals. Little is known 
of the distribution of dioxins or dibenzofurans in 
the environment. 

The purification process developed at the 
Laboratory is based on the strong adsorption of 
dioxins and related compounds by coconut 
charcoal; a patent on the process was filed by the 
Department of the Interior. As a result of the patent 
filing, a project was funded by the U.S. Air Force 
and jointly conducted by chemists from the 
University of Missouri and the Fish-Pesticide 
Laboratory for the cleanup of Herbicide Orange. 
When the feasibility of cleanup was demonstrated 
on a laboratory scale with columns of coconut 
charcoal, the most critical step in the process was 
the percolation rate of the herbicide through the 
charcoal bed. 

Recently, the purification process for Herbicide 
Orange was satisfactorily demonstrated on a pilot 
plant scale by a private chemical company. 
Purification of the stockpile of 2.3 million gallons is 
now pending an environmental impact statement. 
However, an acceptable process for disposing of the 
contaminated charcoal is still needed. 

We believe the purification process will permit 
reclamation of Herbicide Orange worth millions of 
dollars and may have potential for greatly reducing 
dioxin and dibenzofuran contamination in several 
widely used chemicals, thus preventing introduction 
of these toxic contaminants into the environment. 
The affinity of dioxins and related compounds for 
charcoal may have application to some kinds of 
cleanup of these or similar materials accidentally 
released into the environment. 

Patent Filed on New Material for Dioxin 
Adsorption. — The Department of the Interior is 
filing a patent on a new adsorbent developed at the 
Fish-Pesticide Research Laboratory which may 
permit automated cleanup of environmental 
samples. The adsorbent consists of powdered 
charcoal which is held in place on reticulated 
polyurethane foam by strong interactions between 
the charcoal and foam surfaces. Charcoal-coated 
foam has high permeability and its use has already 
increased the efficiency and speed of analysis for 
some toxic industrial contaminants, including 
dioxins and dibenzofurans. 

We are now testing foam-charcoal columns in 
conjunction with an automated gel permeation 
system for the cleanup of pesticides and industrial 
chemicals, which are present in many fish and 


A scanning electron micrograph (300X magnification) of 
several pieces of shredded polyurethane foam with 
particles of AMOCO PX-21 charcoal adhering to the 
surface. The surface of the foam-charcoal complex was 
coated with a 400 A° gold film. Photo by J. A. White. 

wildlife extracts. The tandem combination of this 
system and foam-charcoal columns will enhance 
separation of pesticides and industrial contaminants 
and is readily adaptable to automation of the 
cleanup of a wide variety of environmental samples. 
Dieldrin Residues Cause Closing of Commercial 
Fishery in Iowa Reservoir. — Commercial fishing 
was closed in Coralville Reservoir, near Iowa City, 
when analyses at the Fish-Pesticide Research 
Laboratory revealed that channel catfish from the 
reservoir contained 0.86 Atg/g (ppm, whole body, 
wet weight) of dieldrin. We analyzed several 
samples of channel catfish at the request of Area 
and Region 6 Offices of the Service. The residues of 
dieldrin were high enough to lead us to suspect that 
they may affect channel catfish reproduction. In 
addition, we found relatively high concentrations 
of technical chlordane in the same samples. Because 
of the high residue of dieldrin, several thousand 
catfish scheduled to be stocked in Coralville 
Reservoir by the Service were stocked elsewhere. 
Also, officials of the State of Iowa closed this 
reservoir to commercial fishing after they were 

informed of the results of our analyses. 
Great Lakes Fish Found to Contain Toxaphene. 

— Toxaphene was recently detected in fish 
collected in the Great Lakes. This is one of the first 
reports of toxaphene residues in fish from this area. 
Over 50 samples of sport and forage fish were 
collected and analyzed at the request of the Twin 
Cities, Minnesota, Regional Office. All of the 
samples contained residues of toxaphene. The 
residues ranged from 8.1 Mg/g (ppm, whole body, 
wet weight) in a sample of lake trout from Lake 
Michigan to less than 0.2 jug/g in several species 
collected from Lakes St. Clair, Erie, and Ontario. 
Residues of other contaminants found in the same 
fish included three polychlorinated biphenyls, cis- 
and fra«.s-chlordane, p,/?'-DDT, p.p'-DDD, p,p'- 
DDE, hexachlorobenzene, dieldrin, endrin, and 
heptachlor epoxide. Research with toxaphene at 
the Columbia laboratory has shown that this 
insecticide appears to have no effect on growth and 
reproduction of brook trout at concentrations as 
low as 40 ng/ 1 (parts per trillion). Residues in brook 
trout exposed to 40 ng/1 of toxaphene were about 
0.6 ug/g, considerably less than the concentration 
of toxaphene measured in lake trout from Lake 
Michigan. Additional research is scheduled in fiscal 
year 1977 to confirm and further characterize the 
toxaphene residues. 

Forest Insecticide Residues Detected in Fish 
After Spruce Budworm Control. — Residues of 
three forest insecticides — Matacil, a carbamate, 
and Sumithion and Dylox, both organophosphates 

— were found in fish after the insecticide had been 
applied to several thousand acres in Maine to 
control spruce budworm. Sevin and Zectran were 
applied at the same time, but residues of these 
chemicals were not detected in fish. Over 80 
samples of fish were analyzed during this 
cooperative project with the Forest Service, the 
Atlantic Salmon Investigations and the Boston 
Regional Office of the Fish and Wildlife Service, 
the University of Maine, and the State of Maine. 
Sumithion residues were found in all fish collected 
within 48 hours of its application. Concentrations 
of Sumithion residues in the fish ranged from 0.02 
to 1.21 uglg and averaged 0.25 /ug/g (ppm, whole 
body, wet weight). In general, fish collected 24 
hours after application of Sumithion contained 
higher residues than fish collected 48 hours after 
application. Matacil and Dylox residues were 
found in very few samples and were relatively low. 
For instance, Matacil residues ranged from 0. 1 to 
0.2 /ig/g and the only sample with a Dylox residue 
contained less than 0.1 j/g/g. Toxicological studies 


with these insecticides are discussed elsewhere in 
this report. 

Mirex Residues in Amphibians and Reptiles 
Collected in the Southeastern United States. — 

These animals were collected by personnel of the 
Auburn University Cooperative Wildlife Research 
Unit from areas having a history of repeated Mirex 
applications for eradication of the fire ant. The 
samples analyzed included toads, frogs, turtles, 
lizards, and snakes. Snakes contained the highest 
concentrations of Mirex, averaging 0.15 ug/g 
(ppm, whole body, wet weight), and the incidence 
of contamination was 83%. Other residues detected 
in these animals included heptachlor epoxide, cis- 
chlordane, several DDT isomers and metabolites, 
hexachlorobenzene, benzene hexachloride, toxa- 
phene, dieldrin, endrin, and two polychlorinated 
biphenyls. In general, the residues measured in 
animals collected in this survey were slightly lower 
than those detected in fish from the same region. 


The Role of DDE and PCB's in the Reproductive 
Failure of Lake Michigan Lake Trout. — DDE and 
PCB's are reported to be capable of affecting 
reproduction in fish at levels similar to those found 
in the eggs of adult spawning lake trout from Lake 
Michigan — up to 5 ppm of DDE and 8 ppm of 
PCB's in 1975. Previous work by the Great Lakes 
Fishery Laboratory and the Michigan Department 
of Natural Resources has shown that the 
hatchability and survival of young from con- 
taminated eggs is generally good when they are held 
under standard hatchery or laboratory conditions. 
Little is known, however, about the survival of the 
contaminated fry when they are exposed to ambient 
levels of DDE and PCB in Lake Michigan — 
estimated at between 1 and 10 parts per trillion in 
water and about 0.01 ppm of DDE and 0.3 ppm of 
PCB's in plankton (wet weight). 

In the winter of 1975-76, the Laboratory began 
studies to determine the individual and combined 
effects of DDE and PCB's on young lake trout from 
Lake Michigan. Eggs from spawning fish in the lake 
were incubated in the laboratory and the fry 
exposed for 160 days to DDE and PCB's (Aroclor 
1254) in food and water at concentrations 
approximating those in the lake, and at levels 5 and 
25 times higher than those in the lake. Another 
group of eggs from the lake was hatched and the fry 
reared as controls under conditions of no exposure 

to DDE and PCB's. 

Although studies are not yet complete, early 
observations are that the eggs from Lake Michigan 
lake trout generally hatched well (59% hatch); that 
the proportion of normal fry was high (97%); and 
that there was good survival of normal fry to swim- 
up (94%). Mortality among the young trout 
exposed to DDE — and particularly PCB's — was 
generally higher than in controls, although there 
appears to have been little correlation between 
mortality and the degree of exposure (dose). 
Additional observations on the growth and 
competitive fitness of the young trout are being 
made. Test factors include swimming endurance, 
predator avoidance, temperature preferences, 
respiratory metabolism, and biochemical charac- 

At the beginning of the study, 200 newly hatched 
larvae from each collection of eggs were left unfed. 
We suspected that larvae from highly contaminated 
eggs of Lake Michigan lake trout would die before 
those from hatchery-produced eggs with low 
contamination. This hypothesis proved untrue, 
however, and it was found that the time to 50% 
mortality was 70 days (range 9-100 days) for starved 
larvae from Lake Michigan eggs containing 7.6 
ppm PCB's and 4.8 ppm DDE, and 66 days (range 
7-90 days) for starved larvae from hatchery eggs 
containing only 0.083 ppm PCB's and 0.003 ppm 

Trends in Contamination of Great Lakes Fishes. 
— The need for, and effectiveness of, regulatory 
controls in reducing contamination of the Great 
Lakes is ultimately reflected in the types and 
amounts of contaminants present in fish from year 
to year. Past controls have been extremely effective 
in reducing average concentrations of DDT in fish 
from Lake Michigan and of mercury in fish from 
Lakes St. Clair and Erie. Nevertheless, both of these 
contaminants continue to exceed Government- 
imposed guidelines (action levels) in a few species 
and areas of the Great Lakes (particularly in lake 
trout from Lake Superior). 

Of greatest concern currently are the continued 
high levels of PCB's in certain Great Lakes fishes — 
particularly salmonids from Lakes Superior, 
Michigan, and Ontario. For example, data 
developed by the Great Lakes Fishery Laboratory 
show that average concentrations of PCB's in adult 
fish taken from southeastern Lake Michigan during 
1972-74 ranged from 5.2 to 5.7 ppm in bloaters, 10.4 
to 1 2.2 ppm in coho salmon, and 1 2.9 to 22.9 ppm in 
lake trout. The data showed no decline in PCB 
levels during the 3 years. Thus, voluntary 


restrictions in 1970-71 on the sale of PCB's did not 
result in a decline in PCB concentrations in the 
Lake Michigan fishes sampled. Although analyses 
are not complete on samples offish collected during 
the fall of 1975, initial results for bloaters suggest a 
slight reduction in average PCB concentrations. An 
additional year of sampling, however, will be 
required to determine whether these results 
represent the start of a downward trend. 

Also of concern are the continued elevated levels 
of dieldrin in Lake Michigan fishes. Concentrations 
of this pesticide in the Lake Michigan fishes 
mentioned above have ranged between 0.1 and 0.3 
ppm since the late 1960's with no evidence of a 
decline. The production and sale of aldrin and 
dieldrin were banned in 1974, and we anticipate this 
action will soon be evidenced by a decline in 
average dieldrin residues in the fish. 

Cooperative studies completed in 1975 by the 
International Joint Commission's Upper Lakes 
Reference Group disclosed that although PCB's, 
DDT, dieldrin, and mercury are the major 
contaminants offish in Lakes Superior and Huron, 
several other compounds such as lindane, 
chlordane, chlorobenzenes, octachlorostyrene, 
heptachlorepoxide, naphthalene, phenanthrene, 
toxaphene, and phthalates are also detectable in 
certain species and areas of the two lakes. The 
significance of the presence of these compounds in 
fish is unknown, but the need for continued 
surveillance to detect possible future increases in 
their concentrations is strongly indicated. Recent 
reports of Mirex in Lake Ontario fish at 
concentrations in excess of food guidelines add 
further support to the need for programs capable of 
detecting and controlling the buildup of toxic 
substances in the Great Lakes. 

Effects of Contaminants on the Biochemistry of 
Lake Trout. — Studies were completed on the 
utility and sensitivity of allantoinase (an enzyme 
important in nitrogen catabolism) as an indicator 
of chronic effects of contaminants on lake trout. 
Contaminants under investigation were mercury, 
cadmium, lead, copper, DDT, and PCB's. 
Exposure of allantoinase in vitro to inorganic 
mercury showed that the enzyme extracted from 
acetone powder is about 100% active up to 20 ppm 
of mercury (Hg + ), above which the activity drops 
suddenly. At 30 ppm of mercury, the enzyme is 95% 
inhibited. The concentrations of metals at which 
50% inhibition of allantoinase occurred were as 
follows: 0.21 ppm of lead (Pb ++ ), 0.67 ppm of 
cadmium (Cd ++ ), 0.63 ppm of copper (Cu + ), and 
between 20 and 30 ppm of mercury. On the basis of 

molar concentrations, allantoinase is most sensitive 
to lead and least sensitive to mercury. Allantoinase 
was not affected by DDT or PCB's in vitro at 
concentrations up to 10 and 7 ppm, respectively. 

Twenty lake trout, previously exposed for 28 
weeks in the Laboratory to low levels of PCB's (0. 1 
ppb) in water, accumulated 2.6 ppm of PCB's in the 
liver, which had a mean allantoinase activity of 
0.168 ± 0.0212 (±SE) umol product (min) -' (mg 
protein) -' compared with 20 control fish with a 
mean of 0.1 19 ± 0.0155. This apparent activation 
of the enzyme by PCB's is significant at the 90% 
confidence level. 

Allantoinase activity in the livers of lake trout 
from Lake Michigan was significantly higher than 
in similar samples from Lake Superior. Livers of 
large lake trout (larger than 500 mm) from Lake 
Michigan contained 21 ppm of PCB's, 4.7 ppm of 
total DDT, and 0.94 ppm of mercury, compared 
with 4.5 ppm of PCB's, 1.9 ppm of total DDT, and 
0.69 ppm of mercury in the livers of Lake Superior 
fish. We also observed that allantoinase activity 
was negatively correlated with body length for fish 
from Lake Michigan, whereas no correlation was 
observed for fish from Lake Superior. 

It appears that PCB's, DDT, and mercury, 
possibly acting synergistically with other con- 
taminants, may be the cause of decreased 
allantoinase activity in large Lake Michigan lake 
trout. The significance of this reduction for survival 
of the fish is not known. In vitro assays, including 
kinetic data, provided some indication of the 
mechanism and relative toxicity of the different 
metals. However, the use of allantoinase as a short- 
term indicator of chronic effects now appears to 
have little potential. 


Brown Pelicans in South Carolina Increase in 
Number, Resume Normal Reproduction in Wake of 
DDE Decline. — In 1976, brown pelicans in South 
Carolina numbered 2,500 breeding pairs, a 
substantial increase from the 1,116 pairs present in 
1970, 'when only 945 young were fledged. 
Populations in the pre-DDT era have been 
estimated at 6,000 pairs, with an annual production 
of approximately 7,200. The 1976 population, 
although still less than half the number in the 
historic colonies, now has the potential to increase 
to the limits of the present-day habitat and food 

A long-term study, undertaken jointly with staff 


of Cape Romain National Wildlife Refuge, 
recorded the upward trend during the same 8-year 
period that showed drastic decline of DDE in eggs 
of the nesting birds. Reproductive success increased 
as the population increased, although flooding of 
nests in 1972 and 1974 produced temporary 

Shell thickness increased 8% from 1969 to 1975 
but was still 10% below the pre- 1947 mean. 
Paralleling these changes, DDE residues in eggs 
declined from an average of 5.45 ppm in 1969 to 
1.30 ppm in 1975. 

Brown pelicans are among the species most 
sensitive to DDE-induced shell-thinning; the 
dramatic improvement in breeding success that 
paralleled the decline of DDE completes the study 
and validates the evidence that implicated DDT in 
the reproductive problems of this species. 

Although DDE is the primary shell thinner, 
dieldrin and PCB's present in the eggs may have 
affected embryo survival or other aspects of 
reproduction. Dieldrin residues declined from 1.16 
ppm in 1969 to 0.36 ppm in 1975 and so may have 
contributed to the overall improvement in 
population. PCB's, in contrast, were 6.11 ppm in 
1969 and 6.24 ppm in 1975, fluctuating between 
5.25 ppm and 7.51 ppm in the intervening years. 

Nest Success of Texas Brown Pelicans. — Before 
1920 the Texas coast supported a population of 
5,000 brown pelicans. In 1963 the remnant 
population numbered no more than 100, and since 
1970, fewer than 50 pelicans have been observed 
during the breeding season. Fewer than 30 were 
counted in 1976. Reproduction has been notably 
poor during these years, and recruitment of birds 
from Mexico has failed to compensate. Nest success 
was better in 1976 than in any year since 1963 — 16 
young fledged from nine nests, a reproductive rate 
sufficient to maintain a population. 

The full cause of the poor reproduction cannot be 
determined, but it seems probable that chemical 
contamination of the environment was a contributing 
factor. Shell thickness in 1961 was 15% below the 
pre-1947 measurements, 11% below in 1970, 9% 
below in 1974, and 7% below in 1976. Increasing 
shell thickness in these years suggests the possible 
beginning of improved reproductive success. Eggs 
were not analyzed in the earlier years. In 1970, 
however, DDE in eggs measured about 3 ppm and 
by 1974 about 1 ppm. PCB's declined from 10 ppm 
in 1970 to 3 ppm in 1974. 

Brown Pelicans Prosper in Florida; Problems 
Beset Birds Transplanted to Louisiana. — Surveys 
of Florida pelicans in 1969 showed much less shell 

Mm& - 


Residues of DDE in eggs of brown pelicans have declined 
during the last several years. Improvements in breeding 
success occurred during this period, validating the 
evidence that implicated DDT in the reproduction 
problems of this species. Photo by J. O. Keith. 

thinning and lower organochlorine residues than in 
South Carolina pelicans. Eggshells from the 
Atlantic Coast were 9% thinner than in the pre- 
DDT era and Gulf Coast eggshells were 7.5% 
thinner. Little change occurred by 1974, the last 
sampling period. 

Mature brown pelicans were extirpated in 
Louisiana in the 1960's and did not return. 
Restoration efforts began in 1968 by annual 
transplants from Florida colonies. The pelicans 
began breeding in 1971, and success seemed 

The subtler effects, however, suggest that 
pollution of the Louisiana ecosystems may slow or 
halt improvement. The most critical aspect is the 
steadily declining thickness of eggshells, which 
averaged 0.517 mm in 1971 but dropped to 0.480 in 
1975. This drop represents a 7.2% thinning from 
1971 and is 13.4% below the pre-1947 norm. Shell 
thickness was 0.494 mm in 1976, a slight 
improvement. DDE levels in eggs averaged 1.3 ppm 
in 1972 and 1973, 0.78 in 1975. Dieldrin measured 
0.45 ppm in 1972, 0.64 ppm in 1973, and 1.08 in 
1975. Endrin (0.50 ppm) was also present in 1975. 
In that year, a number of adult birds died in 
Louisiana with lethal and near-lethal levels of 
endrin in their brains. Adult mortality among long- 
lived, late-breeding birds such as brown pelicans 
can adversely affect population survival, com- 
pounding the ill effects. 

New Endrin Problems Identified. — Recent 
work suggests that the insecticide endrin is more 


dangerous to birds than generally believed: (1) 
White pelicans dying in the Tule Lake area of 
California proved to have ample amounts of endrin 
in their brains to account for death. (2) Secondary 
poisoning with endrin was demonstrated both in 
the field and laboratory. Hawks soon died when fed 
endrin-killed prey. (3) Brown pelicans of the 
endangered Louisiana population had endrin as 
well as dieldrin, toxaphene, and other insecticides 
in their brains at death. These chemicals may have 
been the cause of death of some Louisiana pelicans, 
both white and brown. (4) Endrin was present in 
nearly all eggs of brown pelicans in Louisiana. The 
amounts ranged from zero to 2.3 ppm in 1974 but 
were usually around 0.5 ppm (wet weight). The 
significance of these levels for hatchability is not 
known. The egg residues prove, however, that 
Louisiana pelicans commonly take in endrin and 
hold it for some time. 

Endrin residues in pelican eggs and lethal levels 
of endrin in pelican brains suggest that pelicans do 
not lose endrin as rapidly as some animals do. Rats 
lose half of their intake of endrin within 2 to 4 days, 
metabolizing and excreting it rapidly. Experimental 
quail, pheasants, and mallards can break down and 
excrete endrin well enough to live for at least a year 
or two with 1 ppm in the diet. Some mallards can 
tolerate surprisingly large amounts of endrin in the 
diet, which explains why kills of waterfowl by 
endrin have rarely, if ever, been reported from the 

Heavy Metal Residues in Eggs of Black-crowned 
Night Herons Are Measured. — Measurable 
concentrations of seven heavy metals were detected 
in 48 night heron eggs from five Atlantic Coast 
States. Arsenic concentrations were significantly 
greater in samples from South Carolina, Maryland- 
Virginia, and Massachusetts than in samples from 
Louisiana and Florida. Mercury concentrations in 
samples from Massachusetts were higher than in 
samples from Louisiana, Florida, and Maryland- 
Virginia. Elevated levels of arsenic and mercury at 
some localities probably reflect local contamination. 
Mercury was present in some eggs at levels near 
those causing impaired reproduction in ring- 
necked pheasants. Mean concentrations of 
cadmium, chromium, copper, lead, and zinc did not 
differ significantly among localities — they 
probably represent background levels. 

Organochlorine Residues in Eggs of Anhingas 
and Wading Birds. — Eggs from more than 1,300 
clutches of anhingas, herons, ibises, and related 
species were collected from 50 localities in the 
eastern United States during 1972 and 1973 and 

Black-crowned night heron at its nest. Residues of heavy 
metals in night heron eggs collected along the East Coast 
reflected local contamination. Photo by K. A. King. 

were analyzed for organochlorines. Organo- 
chlorine residues, including mirex, were more 
frequently found in eggs from the Great Lakes 
region than in eggs from other areas. Eggs from 
coastal colonies in the Northeast had the second 
highest frequency of occurrence of chemical 
residues, and eggs from coastal areas of the Gulf of 
Mexico had the lowest. DDE was present in 96% of 
the eggs analyzed and PCB's in 61%. Other 
compounds detected were DDD, DDT, dieldrin, 
cw-chlordane, /rorts-nonachlor, and hexachloro- 

Eggshell thinning occurred in anhingas from 
Louisiana and Mississippi (-7.5%); great blue 
herons from Florida (-5.5%) and the Midwest 
(-6.8%); wood storks from Florida (-8.9%); and 
black-crowned night herons from New Jersey 
(-12.3%), Massachusetts (-9.3%), New York, 
Rhode Island, and Connecticut (-7.1%), Ohio and 
Michigan (-5.6%), and Florida, Georgia, and South 
Carolina (-4.6%). 

Wading Birds as Indicators of Environmental 
Quality. — The hypothesis that wading birds are 
indicators of coastal environmental quality and can 
be used as the basis of a biological monitoring 
program was subjected to field tests on the Atlantic 
Coast in 1975 and 1976. Earlier, Patuxent studies 
had shown that wading birds clearly depicted the 
chemical contamination of the coastal ecosystem 
and showed the need for extending the research to 
encompass problems beyond those introduced by 


White ibis, adult and young on nest. Photo by K. A. King. 


Early results have been most promising, but 
several years of study will be required to measure 
the natural variability in colony size, location, and 
species composition as a background against which 
to evaluate changes produced by man-made 

Eight teams of investigators located and 
censused 198 colonies along the Atlantic Coast 
from Maine to Florida. Fourteen species, including 
over a quarter million breeding birds, were 
censused. The number of species in colonies ranged 
from 1 to 11. Colonies with one or two species 
increased, and colony size decreased, from Florida 
to Maine. 

Five teams of investigators studied the reproductive 
biology of nine species in 13 colonies. Mean clutch 
size, the percentage of nests in which one or more 
eggs hatched, and the overall percentage of eggs 
that hatched differed among colonies for some 
species, but no latitudinal gradient was found in 
any of these parameters for any species. 

Identification of the portions of the environment 
of crucial importance to the different species was 




-ft .y 

< \ f 

\ i*V* 


at ' 



Wading bird colonies of the Atlantic Coast are concentrated 
in areas of increasing population and industrial develop- 
ment. Investigations now under way show these birds to be 
effective biological indicators. The map shows locations of 
the 198 colonies found in the first year of the study. 

approached through an analysis of feeding 
behavior. Feeding sites of the great egret, snowy 
egret, and Louisiana heron, located near Beaufort, 
North Carolina, were described by eight environ- 
mental variables: elevation, cordgrass (Spartina 
alterniflora) height, cordgrass density, water depth, 


Young osprey at its nest on the Potomac River, Maryland. 
Biologists from the Patuxent Wildlife Research Center 
have studied the effects of environmental contaminants on 
the reproduction of ospreys on the Chesapeake Bay and 
surrounding areas since 1968. Photo by J. R. Maestrelli. 

water conductivity, water hardness, water turbidity, 
and water temperature. 

Analysis of these variables and of the differences 
in habitat use by the different species will constitute 
the second phase of these studies. 

Chemical Residues in Bald Eagles, 1973-74. — 
Eighty-six bald eagles found dead or dying in 24 
states all contained DDE, and all but two contained 
PCB's. Seventy-five contained dieldrin, four at 
levels high enough to suggest death from dieldrin 
poisoning. Heptachlor and one or more chlordane 
residues were present in more than half the birds. 
Mirex was present in 28. Illegal shooting accounted 
for 25% of the deaths, a smaller percentage than in 
the past. Two eagles died as a result of fights with 
other eagles; one flew into the propeller of a plane; 
six drowned; and three were killed by trappers after 
capture in muskrat traps. 

Organochlorine residues remained high in eagle 
carcasses. Median levels in the 2 years were 1 2 and 7 
ppm for DDE; 0.7 and 0.6 ppm for dieldrin; 23 and 
10 ppm, PCB's; 0.7 and 0.25 ppm, mirex. Highest 
level of DDE was 1 10 ppm; of dieldrin, 14 ppm; of 
PCB's, 820 ppm; and of mirex, 8 ppm. 

Dieldrin Toxicity Enhanced, Lethal Brain Levels 
Lowered, by Presence of Other Chemicals. — 
Eagles found dead in the field frequently contain 
residues of dieldrin in their brains just below the 
levels known to be in the lethal range, and in these 
cases a great many other chemicals usually are 
present in substantial but sublethal amounts. 

An experiment to compare the effects of an 

aggregation of chemicals with those of dieldrin 
alone showed that the effects of a combination of 
chemicals were additive; in fact, the presence of 
other chemicals lowered the levels of dieldrin in the 
brains of dead birds. Chemicals in the mixtures 
were those most often encountered in eagles: 
PCB's, DDE, chlordane, DDT, heptachlor, and 

Birds fed only dieldrin survived longest and had 
the highest levels of dieldrin in their brains. Those 
fed the mixtures survived shorter periods of time 
and had lower levels of dieldrin. None of the other 
chemicals approached diagnostically lethal levels 
determined for them in other studies. Percentages 
of lethal levels of each chemical present, however, 
added up to essentially 100%. 

Bald Eagles in Maine Have Continuing Pollutant 
Problems. — Eggs of bald eagles, collected 
primarily from unproductive nests, were used to 
monitor levels of pollutants and to determine the 
effects of these pollutants on reproduction. 
Productivity of Maine bald eagles has been low for 
many years. Levels of DDE in eggs collected there 
in 1974 and 1975 had not declined from the levels 
found in eggs collected in the late 1960's, even 
though use of DDT has been virtually discontinued 
there since 1970. Dieldrin levels in Maine eggs 
appear to be declining while PCB levels appear to 
be increasing, and most eggshells continue to be 
considerably thinner than normal. 

A preliminary study was conducted to determine 
the source and trends of pollutant levels in foods of 
Maine bald eagles. Fish samples collected in 1974 
generally contained higher levels of PCB's but 
lower levels of DDE than were found in 1966. Gulls 
collected in 1966 contained much higher levels of 
pollutants than were found in fish, indicating that 
birds may be an important dietary source of 
pollutants for the eagles and their eggs. 

DDE Strikes Barn Owl Reproduction; Dieldrin 
Does Not. — DDE at 3 ppm in the diet of captive 
barn owls caused shell thinning, failure to hatch, 
and death of young. Only six young fledged from 
1 14 eggs laid (5. 3%) by adults fed DDE. These birds 
lost clutch after clutch. In contrast, almost 50% of 
the eggs laid by control birds produced surviving 
young. Dieldrin at 0.5 ppm in the diet did not 
produce the same effects as DDE; hatching and 
fledging were as good as those of controls. Owls fed 
DDE laid eggs that averaged 24% thinner shells 
than eggs of controls. 

Residues of Environmental Pollutants Low in 
Chesapeake Bay Canvasbacks. — Canvasback 
ducks collected from Chesapeake Bay during the 


winters of 1975 and 1976 contained low levels of 
organochlorine compounds. DDE (0.10-6.3 ppm) 
and PCB's (<0.5-14 ppm) were detected in almost 
all samples. Dieldrin occurred in 14% of the 
samples. Residues of organochlorines in most 
canvasback eggs were below levels known to impair 
reproductive success in birds. 

Cadmium levels in canvasback kidneys ranged 
from 0.11 to 9.1 ppm. Experimental studies with 
mallards have shown that birds on a chronic dietary 
dosage of 2 ppm cadmium accumulated levels in the 
kidneys similar to levels found in wild canvasbacks. 

Canvasback livers contained lead residues 
ranging from < 0.04 to 1.9 ppm. A few of the birds 
were exposed to elevated levels of lead, but the 
majority reflected only background levels. 

Lead-iron Shot Reduces Lead Toxicity to 
Mallards. — An experimental lead-iron shot 
containing 40% lead was less toxic than commercial 
lead shot to mallards fed a whole corn diet. Higher 
mortality occurred in ducks dosed with lead shot 
compared with ducks given lead-iron shot 
containing comparable amounts of lead. One #8 
lead shot caused 35% mortality in 4 weeks, and 
higher amounts of lead caused nearly 100% 
mortality. Ingestion of one or two #4 lead-iron shot 
caused only 5% mortality during a 14-week period. 
Ducks dosed with 5 lead-iron shot suffered 45% 
mortality compared with 50% mortality for those 
given 16 shot. 

In other studies, the toxicity to mallards of lead- 
iron shot composed of 40 to 60% lead was 
compared with the toxicity of commercial lead shot 
and commercial steel shot. Mortality and body 
weight were directly related to percentage of lead in 
the dose. Survival time, packed cell column, and 
hemoglobin levels were inversely related to the 
amount of lead. Five #4 shot composed of no more 
than 40% lead were relatively nontoxic to captive 
game farm mallards fed a diet of corn. (This study 
was carried out under contract to the Illinois 
Natural History Survey.) 

Hazards of Multichemical Exposure Explored. 
— The possibility of interactions between 
chemicals is much feared but little understood. 
Results of several studies suggest the hazards may 
be real but the problems complex: 

Chlordane and endrin add up in brain to cause 
death: Bobwhites were given nonlethal doses of 
chlordane followed by lethal doses of endrin. 
Others were given endrin alone. The residues of 
endrin in the brains of bobwhites that died after 
receiving both chemicals averaged 38% lower than 
residues in birds that died of endrin alone. The 

Nestling barn owls in a duck blind on the Potomac River, 
Maryland. Studies with captive barn owls have shown 
them to be sensitive to the effects of DDE. Photo by J. R. 

chlordane components clearly had an additive 
action with endrin. 

DDE increases susceptibility to parathion; 
chlordane reduces it: Adult male coturnix were 
pretreated with DDE or chlordane for weeks before 
being challenged with parathion. DDE increased 
the mortality from parathion, but chlordane had a 
protective effect. The two chlorinated hydrocarbons 
apparently had different effects on liver enzymes 
that affect the action of parathion. 

Low levels of methyl mercury intensify the action 
of carbofuran: Explorations of interaction between 
methyl mercury and carbofuran, a commonly used 
pesticide, showed that preexposure to low levels of 
mercury increased the effects of carbofuran on the 
brain. The same result did not occur with 
parathion, a chemical of the organophosphate 

Impact of DDT Spraying in 1974 for Control of 
Tussock Moths. — During June and July of 1974 
more than 400,000 acres of forested land in 
northeastern Oregon, southeastern Washington, 
and adjacent areas of Idaho were sprayed with 
DDT for control of the tussock moth. The Fish and 
Wildlife Service cooperated with the U.S. Forest 
Service to investigate the impact of this single spray 
on raptorial and insectivorous birds that nest on 
treated areas. Three hundred nest boxes were set 
out in and adjacent to spray areas to attract nesting 
American kestrels. Mountain bluebirds and 
common flickers as well as kestrels readily nested in 
the boxes. 

Levels of DDT and its metabolites built up in 
kestrels after the aerial application of DDT. DDT 
residues in blood of birds from the spray areas 
increased almost immediately after spraying and 


Captive kestrels at the Patuxent Wildlife Research Center 
are used in studies to assess the effects of environmental 
contaminants on birds of prey. Knowledge obtained is 
applied to the peregrine falcon and to other comparatively 
rare species. Photo by L. C. Goldman. 

continued to increase the next year. Residues also 
increased slightly in birds on adjacent nonspray 
areas the year after spraying. Residues in eggs of 
kestrels, bluebirds, and flickers followed the same 
pattern observed for kestrel blood. A preliminary 
evaluation indicates that residues in blood of 
kestrels declined during 1976 as compared with 
1975, but were still about fivefold higher than 
prespray levels. Kestrel eggshells from the spray 
areas were 10% thinner than eggshells from 
nonspray areas, although production of fledged 
offspring was almost identical on spray and 
nonspray areas. 

Studies will continue with the kestrel population 
in the future. Additional studies will be concerned 
with accipiter hawks, which also nest in the area. 
Rapid population declines, thin-shelled eggs, and 
reduced productivity have been observed in 
populations of Cooper's and sharp-shinned hawks. 
These bird-eating hawks may be more vulnerable to 
DDT exposure than the more insectivorous species 
studied thus far. 

Effects of New Chemicals on Wildlife in Western 
Forests, — Pilot studies for control of western 
spruce budworm and tussock moth included tests 
of effects on wildlife of four of the newer chemicals 
used to control forest insects: Dylox, Sevin, 
Dimilin, and Orthene. 

Dylox and Sevin-4-oil, which were studied in 
spruce budworm areas, had no observable 
deleterious effects on nest success or population 
abundance of forest birds, and no dead birds were 
found in intensive searches. There were nine study 
plots ranging in size from 1,000 to 2,000 acres; three 
plots were untreated and three each were treated 
with one of the two chemicals. Thrushes, 
woodpeckers, flycatchers, swallows, house wrens, 
sparrows, juncos, and warbling vireos comprised 
the majority of the nesting population. Brain 
cholinesterase depression, which measures the 
effects of chemicals of the types used in these 
treatments, showed little overall change. However, 
during the first day or two after both Dylox and 
Sevin sprays, significant depression occurred in a 
few birds of each of several species. The full 
significance of such changes in terms of susceptibility 
to predation or ability to obtain food remains to be 

Sapsucker nesting inside an aspen tree. Breeding success 
of nesting birds is an important indication of the effects of 
forest insecticides on birds that breed in western forests. A 
tubular device facilitates viewing the nest contents. Photo 
by A. W. Shultz. 


Sevin, Dimilin, and Orthene were tested in 
tussock moth areas. Neither Sevin nor Dimilin 
adversely affected populations or reproduction of 
forest birds. As in the spruce budworm areas, 
however, brain cholinesterase depression was 
measured in a few birds shortly after treatment with 

Orthene, however, had indications of adverse 
effects on birds. Breeding bird censuses showed an 
estimated decrease of six pairs after treatment on 
one plot, although not on another. Several birds 
were found tremoring or with other signs of 
organophosphate poisoning. Brain cholinesterase 
activity was significantly depressed in most species. 
Although overall population effects could not be 
fully evaluated from this single study, there is 
sufficient evidence of hazard to indicate that 
chemicals other than Orthene should be used for 
aerial control of forest pests. 

New Research Evaluates Impact of Petroleum 
Hydrocarbons on Birds. — Major oil spills, which 
oil and kill thousands of birds and disfigure 
beaches, have stimulated public concern and 
resulted in much effort to clean and salvage oiled 
birds. Spectacular accidents, however, contribute 
only a small percentage of the 5 million metric tons 
that are estimated to be the annual global input of 
oil to the oceans. The bulk of the polluting oil 
results from "normal" operations. 

Little attention has been given to the effects of 
chronic low-level oil pollution or to the less easily 
observed effects of major spills. Research initiated 
in 1976 is directed toward understanding the impact 
of such exposure through a series of studies of the 
ecological, physiological, and toxicological effects 
of oil on birds. Results obtained in 1976 suggest the 
possibility of real hazards: 

Trace amounts of oil on mallard eggshells killed 
developing embryos in a first-step simulation study 
of the possible effects of oiled plumage on eggs of 
incubating hens. 

Experimental studies involving 350 eggs showed 
a direct relationship between the amount of oil and 
mortality of the eggs. No embryo survived 
application of 50 ju 1; 2% survived 20 ul; 12% 
survived 10 ul; and 45% survived 5ul. Eighty-eight 
percent of the untreated control eggs survived. Oil 
was applied to the side of the egg, just away from 
the air sac, when embryos were 8 days old. Oil was 
taken into the shell almost instantaneously and did 
not spread over the surface. As a double check on 
whether the action was toxic rather than the result 
of blockage of gas exchange through the shell, two 
additional groups were tested. In one group, in 

which eggs were treated with 50 u 1 of propylene 
glycol, 80% hatched. In another group, in which 
eggs were treated with 50 ul of a mixture of nine 
paraffin compounds found in crude oil, 72% 
hatched. Dosage was carried to an even lower level 
in a second experiment. Application of 1 ul of oil to 
each of 50 eggs resulted in 68% survival compared 
with 98% among 50 untreated controls. One 
microliter of oil represents approximately 0.02 
parts per million. 

Susceptibility to toxic effects of egg oiling was 
greatest at early stages and diminished with age. 

In a study involving 280 mallard eggs, 5ul of oil 
were applied to eggs at 4-day intervals, beginning 
the 2nd day of incubation. The result was 13% 
survival when the oil was applied to the youngest 
group, compared with 80% for controls. Most 
embryos died within 48 hours of oiling. 

Eider embryos were killed by trace amounts of oil 
applied to shells, validating cross-species comparisons 
of such effects. 

In a test involving 200 fertile eggs of mixed ages, 
69% of the embryos survived 20 ul and 92% 
survived 5 ul. Ninety-six percent of the untreated 
controls and of those treated with 20 ul propylene 
glycol hatched. The better survival of eider embryos 
than of mallard embryos appeared to be the result 
of treating eggs of mixed ages; most eider eggs were 
more than 8 days old — the age at which mallard 
eggs were treated. 

Mallard ducks survived dosages of 100, 1,000, 
and 10,000 ppm oil in diets for 6 months and 25,000 
ppmfor 2 months in a small pilot study (16 birds). 
Egg production, however, declined markedly as 
dosage increased. Those fed 25,000 ppm also lost 
weight despite normal food consumption. 

Vanadium, a contaminant that can reach 50 to 
1,400 ppm in crude oil and that may also enter the 
environment as a result of disposal of processing 
wastes, impaired fat metabolism in adult mallards 
at dietary dosage of 1 to 100 ppm. 

Blood cholesterol in drakes increased with 
dosage increase. Nonlaying hens were not affected. 
Laying birds, however, which normally show a 
pronounced decrease in blood cholesterol associated 
with transport of fat to eggs, failed to show this 
decrease. In pilot studies, laying ducks that had oil 
mixed into their diet laid fewer eggs than normal. 

More than 400 clutches ofseabirdeggs have been 
collected for contaminant analysis from more than 
15 Alaskan sites where population surveys are 
under way. Eighteen species are included thus far. 

Development of chemical analytical methodology 
is approaching completion of the first phase. 


Extraction, separation, and identification of oil in 
spiked liver tissues and feed at 20 ppm have been 
successfully accomplished. 

Analysis of animal tissues for oil is difficult 
because of the very large number of compounds 
involved, the metabolic changes of these compounds 
that may occur in warm-blooded animals, and the 
presence of natural hydrocarbons in animal tissues. 
Hydrocarbons in petroleum have such a wide range 
of molecular structure and molecular weights that 
no presently available method of analysis provides 
an accurate assessment of total petroleum 
contamination when considering all possible oil- 
contamination incidents. 

Generalizations have been made concerning 
methods for distinguishing between petroleum 
hydrocarbons and recent native hydrocarbons in 
living tissue but, in fact, only a very few terrestrial 
and marine species from only a few geographical 
localities have been analyzed for their natural 


Field Tests of a Growth Regulator Insecticide. — 

We completed part of a field study to evaluate the 

biologic effects of Dimilin (a potential mosquito 
larvicide) on major pond organisms and residue 
dynamics in largemouth bass, freshwater clams, 
sediment, and water (residue data to be completed 
by Thompson-Hayward Company). Ponds were 
sprayed with either 0, IX, or 4X the recommended 
application rate of Dimilin (0.03 pound active 
ingredient per acre), four times at biweekly 
intervals, and serial samples were taken for 70 days. 
Fish and clams were not affected but daphnid 
populations were inhibited, as indicated from 
counts (per m 3 ) of 1 ,460, 217, and 6 after 0, 1 X, and 
4X application rates, respectively. Densities of 
dipteran larvae similarly declined in benthic and 
periphyton samples. Gastropods were numerous on 
plate samplers but scarce in benthic samples after 
application. Numbers of oligochaetes more than 
doubled in control ponds but declined in ponds 
sprayed with Dimilin. Results of this field test will 
help in developing guidelines for Dimilin applications. 
Water Contamination from an Unusual Source. 
— A source of contamination in water supplying 
hatching tanks that killed striped bass fry last 
spring was traced to Aroclors in the laboratory's 
compressed air supply. These PCB's were 
commonly used in oil-type compressors. Another 
potential source of water contamination was traced 
to Aroclors in cutting oil used in threading and 
cutting steel pipes. 

Coastal and Anadromous Fish 


Because little is known about the routes and rates of 
seaward migration by young Atlantic salmon 
(smolts), a telemetry study was conducted on the 
Penobscot River, Maine, in 1975 and 1976. Tiny 
ultrasonic transmitters were inserted into the 
stomachs of hatchery-reared smolts, before the fish 
were stocked in the Penobscot at intervals between 
mid-April and early June. The sonic signals from 
the fish were detected by a boat-mounted 
hydrophone. In each year, the definite downstream 
movement of smolts began on May 10, and 
appeared to be triggered by photoperiod and water 

temperature. The smolts traveled downstream both 
day and night, stayed mostly in the main current 
and channel, remained within 2 or 3 m of the 
surface, and moved without hesitation from fresh 
to salt water. 

The telemetry study was extended in 1976 to 
include adult salmon returning from the sea and 
migrating upstream in the Penobscot River. Large 
fish were trapped at a fishway, and miniaturized 
radio transmitters were inserted into the stomachs. 
The fish were released and tracked by receivers in 
aircraft and boats. Some fish held position for as 
long as 20 days below dams equipped with 
fishways; others ascended fishways and then 


A fresh-run adult Atlantic salmon being tagged at the 
Union River fishway in Maine in July 1976. The fish will be 
transported to a brood stock holding pool at the Craig 
Brook National Fish Hatchery, East Orland, Maine, for 
spawning in the fall. Photo by M. M. Campbell. 

descended them; and some moved upstream and 
remained there. Most movement occurred at or 
near sundown. 

Postspawning adult Atlantic salmon, known as 
kelts, generally remain overwinter in the spawning 
river before returning to the sea. Only a small 
percentage survive to spawn again. There is 
growing interest, however, in possibilities for 
increasing the survival of kelts that are trapped and 
held as hatchery brood stock. Their return to salt 
water and the resumption of feeding after months 

A fresh-run adult Atlantic salmon being released into a 
brood stock holding pool at Craig Brook National Fish 
Hatchery, East Orland, Maine. The salmon was trapped at 
the Bangor Dam fishway on the Penobscot River in June 
1976. Photo by M. M. Campbell. 

of pre- and post-spawning fast is the subject of a 
Service-sponsored study at the University of 
Maine. For kelts held in captivity, there appears to 
be a need for careful meshing of increasing 
photoperiod in the spring with increasing salinity to 
stimulate appetite and feeding. An imbalance of 
light and salinity may inhibit feeding, and kelts that 
lose about 50% of their prespawning weight usually 

Some Atlantic salmon streams were included in 
the 3.5 million acres of forest land in Maine sprayed 
with insecticides in June to control a spruce 
budworm infestation. Concurrent studies in the 
laboratory and field indicated that there were few 
adverse effects directly on salmon and brook trout, 
but there may have been sharp reductions in the 
stream invertebrates on which the fish feed. 


Enteric Redmouth Disease (ERM). — This 
bacterial disease of salmonids, originally found in 
Idaho in the 1950's, has since been found in all areas 
of the United States and parts of Canada. Some of 
the outbreaks undoubtedly have resulted from 
inter-regional transport of infected fish. 

Recent comparisons have shown that eastern and 
western strains of the bacterium were serologically 
indistinguishable. Morphological and biochemical 
tests were developed for rapid and accurate 
identification of ERM bacteria. In addition, 
fluorescent antibody techniques (FAT) were 
developed for identification of the ERM bacterium 
in infected fish. For the FAT, a fluorescent dye is 
coupled to antiserum specific for the ERM 
bacterium. The ERM bacteria are specific targets 
for the antiserum with its fluorescent dye. As a 
result, in the presence of specific antiserum, 
bacteria fluoresce brilliantly when viewed with 
microscopes having an ultraviolet light source. 
Older diagnostic procedures required 2 to 3 days to 
complete, but the new FAT procedures require only 
l'/2 hours. 

A New Trout Herpesvirus. — This herpesvirus 
was isolated from rainbow trout brood stock that 
had sustained abnormally high mortality after 
spawning. Testing has shown that the virus will 
grow only in rainbow trout cell cultures. Similarly, 
injected virus killed young rainbow trout, whereas 
brook trout, brown trout, and Atlantic salmon 
survived. Japanese investigators have found a 
similar, if not identical, virus killing young kokanee 
salmon, and a joint effort with them has resulted in 


publication of a Fish Disease Leaflet (No. 44) 
describing the virus and its effects on fish. Major 
herpesvirus outbreaks have occurred at two places 
in Japan, but thus far only at the Winthrop National 
Fish Hatchery, Washington, in North America. 
Cleanup operations were put into practice, and 
surveys are being made to learn of other possible 
occurrences of the virus. The virus must be grown at 
temperatures lower than those normally used, and 
prolonged contact with cell cultures is required to 
insure its detection. Rabbit antiserum has been 
prepared against the new herpesvirus, but it has 
only marginal potency. 


Registration of Fishery Chemicals. — A review of 
the chemicals used in fish culture and fishery 
management indicated that many have never been 
properly registered, even though some, such as 
formalin, have been in use for over 100 years. In 
1972 only 13 of the priority fishery compounds had 
some form of registration. By February 1976, four 
of the existing registrations had been upgraded by 
the establishment of tolerances. One compound, 
rotenone, had received an approved label revision. 
Five of the originally registered compounds were 
being studied for reregistration under the new rules 
of the Federal Environmental Pesticide Control 
Act, and 5 new compounds have been registered for 
the first time, bringing the total number of 
compounds registered for fishery use to 18 as of 
February 1976. 

Seven other compounds for use have been 
submitted to regulatory agencies, petitioning 
rulings or exemptions: TFM, formalin, Thanite, 
quinaldine sulfate: MS-222, malachite green, 
calcium hypochlorite, and quinaldine sulfate. 

Included in an EPA reregistration schedule for 
all chemicals are copper sulfate, 2,4-D, Bayer 73, 
Casoron, rotenone, diquat, dibromide, endothall, 
and simazine. Four registered fishery chemicals — 
antimycin, sodium chloride, Terramycin, and TFM 
— have not been scheduled for review. 

Rotenone and Masoten are also subject to 
Rebuttable Presumptions Against Reregistration 
(RPAR), an action which may be rescinded only if 
evidence can be presented showing that no hazard 
exists or that the risk can be reduced to such an 
extent that significant adverse effects are unlikely. 


Basic Characteristics of Biological Filter Operation 
in Salmonid Culture. — Biological treatment of 
salmonid culture water that simulates the natural 
purification of water in streams permits 100% reuse 
of the water. Purification processes occur at water- 
floc interfaces, wherein protected and stable floes 
contain a varied population of living organisms 
ranging from bacteria to nematodes in numerous 
predator-prey relationships within a porous, 
cohesive community. Efficient purification of 
culture water occurs as a consequence of the 
metabolism of the fish wastes by floe organisms as 
flowing water passes around them. A series of 
biofilters provides protected environments for 
specific floe groups to efficiently degrade 
carbonaceous and nitrogenous wastes. In addition, 
the metabolic wastes of one floe organism become 
the food of another. Refractory organic wastes 
(mostly humic substances) persist, coloring the 
water without harming the fish. However, 
physicochemical treatment of the water with ozone 
and activated carbon removes these wastes and 
produces a clear water suitable for aquaculture. 
Two easily separable and disposable filter wastes, 
one liquid and one solid, are produced from the 
combined biological and physicochemical treat- 

Use of Fatty Acids as a Function of Melting 
Point. — Using fatty acids with melting points 
between -78° and +56° C as supplemental fat in 
addition to the basic essential fatty acid require- 
ment, chemists at the Tunison Laboratory of Fish 
Nutrition determined that fatty acids with low 
melting points have no beneficial effect on growth 
of either trout or coho salmon, regardless of the 
resident water temperature, between 6° and 15° C 
(42° and 59° F). Contrary to expectations, short 
chain fatty acids and their triglycerides, which have 
extremely low melting points, inhibited growth of 
fish. The most pronounced effect was exerted by 
butyric acid and by its triglyceride, which at l%of 
the complete feed inhibited growth by 50%. The 
order of growth inhibition was butyrate > acetate > 
hexanoate > octanoate > decanoate > corn oil, 
coconut oil, triolean, and linseed oil. Some of these 
short chain fatty acids are the ultimate oxidation 
products of polyunsaturated oils and therefore at 
least part of the toxicity of such oils that are old or 
have oxidized is caused by the presence of these 
fatty acids. 


Although short chain fats have been reported to 
cause ketosis in mammals, these fish showed no 
evidence of ketosis when tested for plasma acetone. 
Starved fish and those fed zero carbohydrate 
(except as triglycerides) also gave no evidence of 
ketosis — in contrast to mammals, which often 
develop toxic levels of ketone bodies under similar 

Important Minerals in Diets of Atlantic Salmon. 
— Atlantic salmon require dietary phosphorus for 
optimum growth, feed conversion, and bone 
development; however, little is known about the 
value of phosphorus contained in various practical 
feedstuffs. An experiment completed during the 
year showed that salmon used phosphorus in meat- 
bone meal and phytin (the major form of the 
element in plants) 90 and 0% as effectively as the 
phosphorus contained in inorganic phosphate. 

A study with diets containing soybean meal as a 
major source of protein showed that fry required 
supplemental calcium, magnesium, and potassium. 

Amino Acids Critical to Nutrition of Atlantic 
Salmon. — Young Atlantic salmon were seen to 
require a unique balance of dietary amino acids, 
necessary not only for protein synthesis and normal 
growth but also for prevention of abnormally high 
mortalities similar to those generally experienced in 
cultural operations. 

Further dietary studies showed that commercial 
soybean meal could replace most, if not all, fish 
meal in salmon diets, provided that five amino acids 
were added to simulate the amino acid balance in 
trout eggs. Further experiments demonstrated that 
various other amino acid mixtures, beyond these 
five, gave no further improvement — thereby 
indicating a "near-maximum effect" with the 
original five. 

Enzymatic analyses showed that levels of the 
enzyme that degrades the amino acid arginine in 
various fishes of similar size, fed the same diet, were 
lowest in Atlantic salmon and brown trout, 
intermediate in brook trout, and highest in rainbow 
trout. Such enzyme levels may be directly related to 
the quantitative requirements of these fishes for 
dietary arginine. 

Specially Processed Soybeans as a Protein for 
Salmon. — Experiments with coho salmon showed 
that full-fat soybeans given heat treatment could 
supply the bulk of the dietary protein in starter and 
grower diets if they contained 20 and 10% fish meal, 
respectively. Such soybeans also have potential for 
economical use in diets of Atlantic salmon. 

Additional Heat Treatment Improves Soybean 
Meal as a Source of Protein for Salmon. — 

Previous experiments suggest a fairly high potential 
for the use of commercial soybean meal (SBM) as a 
major source of protein in diets of Atlantic salmon. 
However, nutritional observations suggested that 
SBM may be currently underheated. Chemical 
binding tests with many different samples of SBM 
correlated very well with degree of heat treatment 
applied in the laboratory. Binding tests on many 
different samples of commercial SBM showed a 
wide variation in the range of heat treatments. 
Therefore, nutritional studies were conducted that 
confirmed that many samples of SBM were 
underheated, causing growth depressions of 20 to 
30% in salmon. Parallel cooperative studies with 
poultry gave similar results. However, these initial 
studies measured responses under limited dietary 
conditions, which need to be expanded to 
determine the influence of various supplements of 
amino acids to SBM on the nutritional response to 
added heat treatment. If consistent results prove 
that the poultry industry (which exerts a powerful 
economic influence on the processors of soybeans) 
could benefit from additional heat treatment, as 
would fish culturists, it may be possible to effect 
changes in the processing of SBM that would 
benefit both groups. 


Ozone Studies. — High-quality pathogen-free 
water is essential for the successful operation of 
hatcheries. Ozone treatment has potential value as 
a disinfectant for water and is currently being used, 
or is being considered, as a replacement for chlorine 
in municipal water supplies, sewage treatment, and 
nuclear power plant cooling systems. The effect of 
the chemical on fish pathogens and fish must be 
identified before its use becomes more widespread, 
to ensure protection of the fish resource. 

A concentration of 0.01 ppm ozone inactivated 
enteric redmouth disease (ERM) and Aeromonas 
salmonicida (furunculosis) in 0.5 and 10 minutes, 
respectively, in phosphate-buffered distilled water. 
A residual of at least 0.05 ppm chlorine was needed 
to cause a comparable kill in 10 minutes. In soft 
lake water a chlorine residual of 0. 1 ppm rapidly 
inactivated both pathogens but in hard water A. 
salmonicida was more resistant. Ozonation of the 
two lake waters at 90 mg 3 /h per liter (equivalent 
to a 0.0 1 ppm residual in ozone demand-free water) 
destroyed both pathogens within 10 minutes. 

The ERM bacterium survived through 20 days at 
20° C in either soft or hard lake waters, whereas A. 


salmonicida survived for only 2 days. This indicates 
that disinfection of soft water might not be 
necessary for furunculosis, provided the hatchery 
intake reservoir allows a 1- to 2-day detention time. 
For ERM control, however, treatment would be 
necessary to remove this pathogen. 

Under laboratory conditions, in phosphate- 
buffered distilled water, less than 0.01 mg/1 ozone 
was required to kill the virus of infectious 
hematopoietic necrosis (IHN) within 30 seconds. 
Ten times this much chlorine (0. 1 mg/1) was needed 
to destroy IHN virus within 30 seconds or 
infectious pancreatic necrosis (IPN) virus within 2 

In both soft and hard lake waters, ozone applied 
at the rate of 70 mg 3 /h per liter completely 
destroyed IHN within 10 minutes; however, 
exposure to 90 mg 3 /h per liter caused a marked 
reduction but not total kill of IPN virus. A0.2-mg/l 
chlorine residual inactivated IHN and IPN in 0.5 
and 10 minutes, respectively, in soft lake water but 
had no effect in hard lake water. 

The IHN virus survived for less than 2 weeks in 
phosphate-buffered distilled water at 20° C but 
survived almost 7 weeks in the two lake waters. IPN 
virus survived well in all three water types, suffering 
only a slight reduction after an 8-week holding 

In summary, the IHN virus is more easily 
destroyed by both ozone and chlorine than is the 
IPN virus. If the water is left untreated, IPN titers 
remain high for at least 2 months but IHN dies out 
completely, even in hard water. 

Standard Methods and Interpretation for Fish 
Health. — A manual of standard methods has been 
prepared that includes interpretive tables useful for 
assessment of the effect of environmental stress on 
the health of hatchery and native fish populations. 
The following methods have been included: blood 
cell counts (erythrocytes, leukocytes, thrombocytes), 
clotting time, hemoglobin, hematocrit, methemo- 
globin, plasma, lactic acid, Cortisol, glucose, 
osmolality, and total protein; nitrite and ammonia 
in water; and glycogen in liver and muscle. 

Nitrite Toxicity. — The prevention and 
treatment of nitrite toxicity is an important 
consideration in fish production at hatcheries 
where water is reused. The maximum nitrite 
exposure that juvenile steelhead trout can tolerate 
over a rearing season with no methemoglobinemia 
or decreased resistance to stress, and no adverse 
effect on ability to convert from fresh to salt water, 
is not known, and guidelines are needed for water 
reuse in hatchery operation. 

Groups of steelhead trout chronically exposed to 
nitrite at levels up to 200 ppb for 6 months in soft 
water at KFC suffered no significant blood 
changes, were equally resistant to standardized 
handling and crowding stress, and converted to salt 
water normally. Peripheral blood smears and 
anterior kidney imprints of the fish exhibited no 
significant changes. 

Antidotes to nitrite toxicity were tested with a 
balanced salt mixture and a 96-hour LC50as the 
challenge. Toxicity was greatly reduced as water 
hardness increased over the range of 10 to 300 ppm. 
Since pH automatically increases as water hardness 
increases, the effect of pH alone was tested; it was 
found that increasing the pH (from 6.0 to 8.0) also 
gave substantial protection, especially to small fish. 

The results of this study suggest that mineral 
additions might be helpful and also that water 
chemistry should be taken into account in site 
selection for future water reuse hatcheries. 

It can be expected that biological filters will 
occasionally fail and that nitrite poisoning of fish 
will result. Extensive testing showed that as little as 
0.01 ppm methylene blue, acting as a pseudo- 
hemoglobin, gave protection against nitrite 
poisoning. Methylene blue did not damage the 
biofilters, and might be a practical treatment for 
acute intoxication. 

Studies on Smoltification. — Research was 
conducted for the past several years on the role of 
ATPase in smoltification. Conclusions reached 
from results of these investigations are summarized 
as follows: (1) Transformation from parr to smolt is 
accompanied by an increase in sodium /potassium 
gill ATPase activity in steelhead trout. (2) External 
stimuli, such as photoperiod or water temperature, 
which affect the timing or degree of smoltification, 
likewise affect the ATPase activity. (3) Gill ATPase 
activity was elevated in all seaward migrants tested 
but generally was not elevated in nonmigrants. (4) 
Treatment or conditions which adversely affect the 
elevated ATPase activity associated with the smolt 
stage may also inhibit migratory movement and 
adaptability to salt water. 

Additional studies were initiated to test the 
effects of adding salt to the diet fed to fall chinook 
salmon, feeding Terramycin 50 at standard levels to 
the same species of fish, and exposing steelhead 
trout to light and temperature changes. We also 
monitored stocks of coho salmon at two Federal 
and one State fish hatcheries for ATPase/ migration 
activity. Results of these studies follow: (1) The 
addition of salt increased ATPase activity in fall 
chinook salmon, as well as survival in salt water. (2) 


ATPase activity and saltwater survival of chinook 
salmon increased with size of fish. (3) Feeding 
Terramycin had no detrimental effect on ATPase 
activity or saltwater survival. (4) Under experi- 
mental conditions parr-smolt transformation in 
yearling steelhead trout was accelerated by an 
advanced photoperiod schedule. (5) Exposure of 
migrating steelhead trout smolts to water 
temperatures of 56° to 57° F for 20 days resulted in 
serious impairment of migratory behavior and in a 
reduction of gill ATPase activity. (6) Migration 
tests and ATPase measurements indicate that 
steelhead trout should be reared to a length of 
about 16 cm or larger to obtain a high percentage of 
transformation to smolts. (7) Gill ATPase activity 
was correlated with parr-smolt transformation of 
coho salmon at the three hatcheries; time of 
occurrence varied among the three populations. (8) 
The warmest water produced the earliest coho 
salmon smolts, and there was some indication that 
wide daily temperature fluctuations in cold water 
hastened transformation. 

The results of the ATPase studies have 
established the importance of ATPase measure- 
ments in determining smolt condition. 

Sublethal Effects of Sediment Exposure. — 
Acute and chronic bioassay tests with juvenile coho 
salmon in a flow-through system were conducted to 
assess the impact on fish of suspended sediment 
from a dredging operation. A 24-hour exposure to a 
1% suspension of sediment obtained from the 
dredging project caused mild physiological damage 
to the gills of juvenile coho salmon. It also caused a 
mild, but significant, stress response, recovery from 
which required about 3 weeks. 

A chronic 30-day exposure to 70 ppm of the 
sediment did not cause a stress response. There was 
more extensive histological damage to the gills, but 
no interference with physiological function of the 
chloride cells. 

Inheritability of Resistance to Infectious 
Hematopoietic Necrosis (IHN) Disease. — 
Diseases can be controlled by prevention, 
treatment, or selection of individuals with natural 
disease resistance. Since an inheritable trait to IHN 
resistance may exist in natural populations offish, 
it is important that the level of this inheritance be 
determined. This information would permit an 
evaluation of the possibility of selective breeding of 
fish for resistance. 

Eggs from 16 mature female sockeye salmon 
taken from the spawning grounds were fertilized by 
a single male per female. Subsamples of the 
resulting fry were challenged with IHN virus 

monthly for 4 months. There was a great variation 
(50-100% mortality and 9-14 days to death) in the 
susceptibility of families of sockeye salmon to the 
disease. These differences were constant within 
each family over the test period. At the end of the 4 
months the fish were pooled in susceptible and 
nonsusceptible groups. The pooled groups were 
then challenged for an additional 6-month period. 
At the end of this time the results indicated that 
susceptibility or nonsusceptibility was the same as 
previously, but time to death increased by about 
25% in both groups. 

The results indicate that resistance is genetic and 
inheritable at about a 30% level of inheritance. 

Infectious Hematopoietic Necrosis (IHN) 
Disease Studies in Alaska. — Studies in Alaska 
indicate a widespread distribution of IHN virus in 
all sockeye salmon populations. Although the virus 
was found in all localities where fish were tested, 
prevalence differed among stocks of fish and 
between sexes. 

Females had a significantly higher carrier rate 
than males. Carriers did not significantly differ 
from noncarriers in size, and the association of 
carriers with age class was equivocal. There were no 
detectable anti-IHN antibodies in the serum or 
gonadal fluids of carriers or noncarriers. The virus 
was not detected in sockeye salmon smolts or 
indigenous nonsalmonid species from a lake 
included in the studies. 

Disease Control. — Disease can be controlled by 
preventing it, immunizing the host against the 
causative agent, treating the diseased animals, 
manipulating the environment to inhibit the agent, 
and by other means. 

The effect of various environmental conditions on 
the survival of IHN virus was tested. Dehydration 
of the virus from water at 4° and 10° C resulted in 
partial inactivation, but dehydration from Hank's 
Balanced Salt Solution (HBSS) and homogenized 
fish tissue resulted in total loss of virus activity 
within 7 days. Survival was not affected by pH 
between 6 and 8, but virus activity was significantly 
reduced at pH 5 and 9. Water hardness from 20 to 
250 ppm (as CaC0 3 ) also did not significantly 
reduce virus activity, but salinity distinctly affected 
virus survival. Storage in artificial seawater, filtered 
ocean water, HBSS, and Earl's Balanced Salt 
Solution (EBSS) equally reduced virus titers. 
Deionized water and EBSS and HBSS supple- 
mented with protein showed sparing effects. 
Survival of IHN virus was inversely proportional to 
HBSS concentration; survival was best when the 
virus was frozen in media supplemented with 10% 


calf serum. Viral activity decreased with an increase 
of temperature; survival was best at -70° , -20° , and 
4° C and poorest at Iff 3 , 15°, 21°, 28° and 32° C. 
Freezing and thawing of IHN virus had no effect if 

the medium contained 10% protein, but freezing the 
virus in deionized water resulted in a significant loss 
of infectivity. 



Captive Whooping Crane Produces Offspring; 
More Hybrids Produced. — This proved to be a 
banner year for the whooping crane program at 
Patuxent. The number of pairs producing eggs 
doubled from one to two, and in spite of an 
unseasonable heat wave in April that retarded 
reproduction in most of the cranes, they laid a total 
of five eggs, up from three in 1975. A weak chick 
hatched from the first-laid whooper egg on May 5, 
1976, and in spite of nearly continual difficulties, it 
survived, the first to do so from parents raised in 
captivity. Thus, a major goal of this program — to 
successfully produce and rear a crane in captivity — 
has been realized, though artificial incubation 
procedures with whoopers are yet to be perfected. 

A second goal, to reestablish wild flocks from 
captive stock, took a step toward realization when 
two eggs were taken to Grays Lake National 
Wildlife Refuge where they were placed under a 
preselected pair of sandhill crane foster-parents. 
Although the two eggs were taken by predators at 
Grays Lake, the program appears feasible, and 
plans are well advanced for a continued effort in 

Looming over the efforts to reintroduce 
whooping cranes at Grays Lake is the ever-present 
possibility of imprinting: will whoopers raised by 
sandhills recognize and mate with other whoopers 
or will they select mates from among the large 
flocks of young sandhills? If the latter occurs, it is 
important to know whether hybrids could be 
produced, what they might look like, and whether 
they would be fertile. To answer these and other 
questions, a captive female greater sandhill crane 
was artificially supplied with semen from a 
productive whooper. Three eggs laid by this female 
hatched, and the chicks are being carefully studied. 

They show characteristics intermediate between the 
two parental types and would be very easy to 
identify in the wild. The young chicks resemble 
both parents in body conformation, but the 
characteristic brown plumage of the whooper chick 
predominates and the legs are black. By fall, white 
plumage replaces much of the brown in other parts 
of the body, but a light gray is obvious along the 
back and near the base of the tail. By the next 
summer, most of the bird is light gray to white, the 
legs are dark, and parts of the crown are red. The 
black cheek patch, characteristic of the whooper, is 
absent in the nearly white bird. The reciprocal cross 
using sandhill semen instead of whooper semen 
may result in a phenotype different from that 

Patuxent began this investigative period with 
seven pairs, four unmated birds hatched in 1974, 
and two extra females. Meanwhile, male whoopers 
in San Antonio Zoo, and in Audubon Park Zoo, 
New Orleans, awaited mates. Through cooperative 
loan agreements, the two females were provided as 
mates for two of these males: one female was sent to 
join the famous "Crip" in San Antonio, and 
another, "Tex," was sent to the International Crane 
Foundation, where a week later a male from New 
Orleans arrived to join her. The birds at the 
Patuxent Center in 1974 formed two loose pairs 
and will be placed in breeding pens constructed for 
them this year. Thus, the number of captive 
whooping crane pairs increased from 7 to 1 1 in the 
past year, and the total captive population is only 
slightly smaller than the entire number of breeding 
birds in the wild 9 years ago when this program 

Black-footed Ferret Not Seen in Field for 2 
Years. — Black-footed ferrets were not observed on 
study areas in western South Dakota for the second 
consecutive year, although surveys were more 
intensive. The lack of ferret observations is difficult 


Female whooping crane incubating at the Patuxent 
Wildlife Research Center. Photo by C. B. Kepler. 

to explain, and the failure to find them in formerly 
occupied areas is cause for concern. The number 
and size of prairie dog towns have increased 
substantially in recent years, and more time must be 
expended on each area to confirm the presence or 
absence of ferrets. Also, landowners who readily 
reported ferret sightings in the past are now 
reluctant to do so. They fear that the reported 
presence of ferrets on their lands will jeopardize 
Government-assisted programs for controlling 
prairie dogs. Meanwhile, prairie dog control is 
being practiced extensively on privately owned 
lands and on Indian reservations. Several prairie 
dog towns in Mellette County, South Dakota, 
previously occupied by ferrets, have been treated by 
landowners or tenants. 

First Breeding of Black-footed Ferrets in 
Captivity. — Procedures developed for polecats by 
Soviet scientists were used in attempts to breed 
black-footed ferrets at the Patuxent Center. 
Breeding attempts were initiated when the two 
females were in peak estrus. After a 42-day 
gestation period, three neonates were observed in 
one female's pen. However, they were either killed 
by the female or died as a result of maternal neglect. 
Only minimal precopulatory behavior occurred 
with the other female, breeding was not observed, 
and no young were produced. Efforts to breed this 
female were terminated after 1 1 days, when she was 
no longer in breeding condition. European polecat 
females will be used as surrogate mothers during 
the 1977 breeding season if any litters of black- 
footed ferrets are produced. 


Hybrid whooping crane x greater sandhill crane chicks 
approximately 5 months of age, produced by artificial 
insemination of agreatersandhill crane female with semen 
from a male whooping crane. Photo by G. F. Gee. 

Black-footed ferret in prairie dog town, Mellette County, 
South Dakota. Photo by C. N. Hillmarj. 

Timber Wolves Increase in Northwestern 
Minnesota. — Legally protected in 1974, for the 
first time the wolf population of northwestern 
Minnesota has responded dramatically. In a 1,000- 
square-mile study area in that region, wolf numbers 
increased from an estimated one per 30 square miles 


in 1974-75 to one per 17 in 1975-76. Although 
poaching continues, the kill of wolves by humans 
has declined considerably. As a result, the survival of 
pups, dispersal of maturing animals, and colonization 
of new areas by dispersers have all greatly increased. 

Displaced Depredating Wolves Tend to Seek 
Agricultural Areas. — Wolves preying on livestock 
in north-central and northwestern Minnesota were 
livetrapped, translocated to wilderness areas of 
northeastern Minnesota, radio-collared, and 
released. Generally, they headed west to south from 
the release point, and many frequented farming 
areas. At least two wolves settled near new farms 
and continued preying on livestock. One of these 
was retrapped and removed to another location. 
The other was not recaptured despite intensive 

Eastern Pine Marten Proposed for Endangered 
Species List. — Observations and accidental 
captures of martens in traps set for other species 
have increased in recent years. From 1970 through 
1976, 41 martens were caught in Minnesota, and 9 
were sighted. This apparent increase in marten 
abundance is probably a natural extension of the 
growing population of martens in neighboring 
Ontario, which began to expand in the 1960's. It is 
aided by a maturing forest in Minnesota that is 
beginning to revert to conifers. The greater 
numbers of martens have drawn the attention of the 
public and of conservation groups, which have now 
proposed that the subspecies be placed on the 
endangered species list. 

California Condors Continue to Decline. — The 
numbers of California condors have continued to 
decline as a result of their low annual production, 
averaging less than two young per year. Biologists 
conclude that the total population has fallen to less 
than 50 birds. In 1976 there was confirmed 
production of only one young. 

Supplemental feed (animal carcasses) has been 
provided for California condors almost continuously 
since November 1974. Condors, in low numbers, 
fed on many of the animal carcasses placed for 
them, but with no obvious changes in nesting or 
other use of the Sespe Condor Sanctuary. Cause of 
death of an immature California condor found in 
November 1974 was undetermined. One of the wild 
condors was brought into captivity after having 
been found shot in the wing, but it died after 
surgical removal of the injured limb. 

Efforts to Reestablish Masked Bobwhites Take 
New Directions. — During each of the past 2 years 
over 2,000 masked bobwhite quail chicks or eggs 
have been shipped to the Arizona Field Station at 

Tucson in attempts to reestablish this subspecies in 
southern Arizona. Seven different techniques for 
reintroducing the endangered masked bobwhite 
were tested in 1975 with one common goal — to 
produce birds capable of surviving in the wild. The 
two most promising methods were used in 1976 to 
release over 850 birds in the wild. 

A "call-box" conditioning method has been 
devised in which 6-week-old birds from captive 
stock are introduced to unprocessed seed mixtures 
to simulate wild quail foods and are then placed in 
covey-sized groups (10-15 birds) in a call-box. (The 
call-box is divided to allow the birds released from 
one side to return to the box through funnels on the 
other side.) After being kept in the call-box for 2 
days, some of the birds are released, allowed to 
wander at will, then "called" into the other side by 
the covey calls of the retained birds. After the birds 
have been released and recalled to the box several 
times, they are then harassed by dogs and persons 
on foot. When behavior of the birds resembles that 
of wild birds, they are transported to release 
locations and set free. Some 130 birds were released 
by this method, and results are encouraging. 

In a second method, foster-parents were 
provided. Trials were made using sterilized male 
Texas bobwhites, male and female Gambel's quail, 
a male scaled quail, and call-box trained masked 
bobwhite males, females, and pairs as foster- 
parents. Over 300 chicks were released with quail 
foster-parents. The more promising results were 
produced by assigning 10 chicks (4-10 days old) to 
the male Texas bobwhites, Gambel's quail, and 
scaled quail. Because of potential interspecific 
imprinting and other possible behavioral problems, 
adoptions were restricted to Texas bobwhite quail 
in 1976. 

A male Texas bobwhite, upper left, leaves the release box 
with a brood of adopted masked bobwhite chicks 
produced at the Patuxent Wildlife Research Center. Photo 
by D. H. Ellis. 


Young Florida everglade kites in artificial nest structure in 
cattails, Lake Okeechobee, Florida. Kite nests located 
insecurely in vegetation threatened by high water or wind 
have been successfully moved into these artificial 
structures and the young have fledged. Photo by P. W. 
Sykes, Jr. 

Female Florida everglade kite returning with apple snail to 
nest containing two kite chicks, headwaters of the St. 
Johns River, Florida. Photo by P. W. Sykes, Jr. 

In another release method, masked bobwhite 
eggs are placed in the nests of other native quail. 
Only a small trial of this method was possible; 15 
eggs were placed in one scaled quail nest. Ten eggs 
hatched, and masked bobwhites were seen in a 
scaled quail covey in the fall. This method is 
potentially valuable, but more wild nests must be 
found before a suitable trial can be made. Chicks 
that were newly hatched or no more than a few days 
old were placed with broody bantam hens, who 
raised the young in a semidomestic state at the 
Arizona Field Station headquarters. This method 
proved unsuccessful in trials with 61 chicks. 

Survival success of the released birds cannot be 
properly evaluated until early in 1977; however, as 
of September 1976, a few coveys appear to be 
established and thriving in the wild. Some of them 
have been fending for themselves for over 2 months. 
Meanwhile, observations of masked bobwhue 
numbers in Sonora, Mexico, indicate that the 
condition of the only remaining wild populations is 
worsening. Establishment of a refuge or manage- 
ment area now appears necessary to prevent 
complete extirpation of masked bobwhites south of 
the border. 

Florida everglade kites resting during mid-day on the 
Loxahatchee National Wildlife Refuge, Florida. Photo by 
P. W. Sykes, Jr. 

Endangered Clapper Rail Continues to Decline. 

— The population estimate of the light-footed 
clapper rail in California has been revised 
downward as a result of continuing surveys. 
Probably not over 300 light-footed clapper rails still 
inhabit 14 remnant salt marshes along the southern 
California coast. 


The Status of the Everglade Kite in Florida. — 

Annual censusing each fall (1969-75) has averaged 
92 Everglade kites. The population has remained 
relatively stable at this low level with fluctuations 
from 65 to 120 during the period. A total of 110 
birds were seen on the 1975 census. Sixty-four 
nestling kites have been color-banded since 1968. 
The oldest known banded kite surviving in the wild 
is now 8 years old. How long they may be expected 
to live has not been determined, although closely 
related South American snail kites in captivity at 
the Patuxent Center are 1 1 years old. 

Since 1972, most nesting activity has been at 
Lake Okeechobee. In 1976, there were 23 nests on 
the lake, 10+ in Conservation Area 3A (CA3A), and 
1 at Loxahatchee National Wildlife Refuge. This is 
only the second time since 1968 that kites have been 
found nesting in CA3 A. For the last 9 years, 42% of 
the nesting attempts have been successful. These 
nests produced an average of two young each. 
Nesting failure can be traced to at least 10 different 
causes, predation being the major problem. 

Out of approximately 2.5 million acres of 
freshwater marsh, about 15-16% is known to have 
been used by kites since 1967; not more than 10% is 
estimated to be used in any 1 year. In a drought year 
this percentage is still further reduced. Lake 
Okeechobee and southern and eastern CA3A are 
the most heavily used areas at present. Under 
existing conditions, all habitat in Florida is 
considered marginal for kites on a long-term basis. 
This precarious situation can be corrected through 
land acquisition, habitat development, and 

Hawaiian Forest Birds Inventoried. — Patuxent 
biologists worked closely with the Pacific 
Endangered Species Coordinator and cooperators 
in planning and carrying out the first comprehensive 
inventory of Hawaiian forest birds in the Ka'u 
forest on the lower southeast flanks of Mauna Loa, 
island of Hawaii. Forest bird census stations 
established on transects in the Ka'u forest were 
visited by survey teams following a rigorous 
schedule and equipped with tents and backpacks. 
The survey was completed in 4 months, May 
through August 1976, and the findings are being 
analyzed and prepared for publication. The 
techniques used are expected to be generally 
applicable for future surveys of forest birds 
elsewhere in the Hawaiian Islands, although some 
modification of design may be necessary for special 
situations. A by-product of these surveys will be a 
list of management recommendations that will 
include proposals for land acquisition. 

Substantial Gain Reported for Wild Puerto 
Rican Parrots. — The wild population of Puerto 
Rican parrots (Amazona vittata) experienced two 
unusually good breeding seasons in 1975 and 1976. 
Six young fledged from five active nests in 1975 and 
eight young fledged from four active nests in 1976. 
The production of young now seems strong enough 
to balance mortality, and the wild population has 
finally halted its decline, at least temporarily. As of 
June 1 976 there were 22 parrots in the wild, the first 
time the population has exceeded 20 individuals 
since 1969. However, the age structure of the 
population is now skewed heavily toward 
immatures — the number of breeding pairs has not 

Part of the increase in reproduction can be 
attributed to the acceptance by parrot pairs of three 
artificially constructed nest sites. It appears that all 
mature pairs laid eggs in both 1975 and 1976 and 
that the problem of too few nest sites is now solved. 

Since 1973, nest success has averaged better than 
70%, a distinct improvement from the 20% 
characteristic of these parrots for years prior to 
intensive management. Improvement in nest 
success is due largely to management efforts to 
improve nest sites (particularly keeping them dry 
through the breeding season) and to reduce the 
impact of predation by pearly-eyed thrashers 
{Mar gar ops fuscatus). Thrasher predation on eggs 
and young of parrots has been reduced by three 
basic techniques: (1) Parrot nests were sedulously 
guarded during the critical early stages of the 
breeding cycle. Watchers in blinds shot or 
frightened away intruding thrashers. (2) Parrot 
eggs were artificially incubated at the field station. 
The wild pairs were kept active on plaster of paris 
eggs during the incubation period. Nestling parrots 
were returned to the nests in the wild. In 1975, the 
value of this technique was clearly demonstrated at 
one nest in which the plaster eggs were extensively 
damaged by thrashers. (3) Parrot nests were 
modified to make them unattractive to thrashers, 
and alternative sites for thrasher nests were 
provided near the parrot nests. Several parrot nests 
were deepened beyond the depth preferences of 
thrashers, and thrasher pairs accepting nearby 
shallow nest boxes effectively defended the parrot 
nests from other thrasher pairs prospecting for nest 
sites. With the apparent success of this technique in 
1976, all parrot nests are now being deepened to 
appropriate depths and thrasher boxes are being 
placed nearby in hopes that this method may prove 
to be the most efficient and effective solution to the 
thrasher problem. 


Young Puerto Rican parrot close to fledging from a 
human-excavated nest site in Luquillo Forest. This 6-foot- 
deep hole was the first nest in recent years free from 
pressure of pearly-eyed thrashers. Photo by H. Snyder. 

Since 1973 at least two and possibly as many as 
six successful parrot nests would have been lost to 
thrasher predation if the precautions described 
above had not been employed. Thrashers have 
destroyed only one parrot egg during these years, as 
far as we know. 

As of 1976 the captive Puerto Rican parrot 
population stands at 1 1 birds. No reproduction has 
yet occurred in captivity, although several infertile 
eggs have been laid. All captives taken in 1975 were 
parrots that would not have survived in the wild 
because of botfly parasitism or nest desertion. No 
new captives were taken in 1976. 

Puerto Rican Boa May Not Be Endangered. — 
Records accumulated in the last few years suggest 
that the Puerto Rican boa is far more common than 
was earlier supposed. The species is present in a 
wide variety of second-growth habitats in all major 
regions of the island. Because of its secretive habits 
the species is not easy to observe, and most records 
are of boas crossing or killed on highways or 
discovered by laborers clearing brush. The 
widespread distribution of recent sightings and the 
fact that almost all rural people interviewed across 

Two-week-old Puerto Rican parrot nestling with a neck 
wound received from a pearly-eyed thrasher. This chick 
recovered and eventually fledged successfully. Photo by 
N. Snyder. 

the island have had recent personal experience with 
the species can only mean that it is reasonably 
common. It probably should be withdrawn from 
the list of endangered species. 

Peregrine Falcon Search in Arizona Reveals 
Significant Numbers of Adult Birds. — In 1976 a 
comprehensive search was made to determine the 
occupancy of over 40 historic summering or 
breeding sites of peregrine falcons in Arizona. Most 
sites are now vacant, but 12 sites had one or more 
adult birds in 1975 or 1976. A few immature birds 
have also been observed. Most of the active sites are 
so remote that the nesting cliffs have not been 
identified. Arizona appears to have a large share of 
the remaining scant breeding population of the 
American peregrine falcon and could contribute 
significantly to restoration efforts. 


Effect of Dissolved Solids on Cutthroat Trout and 
Cui-ui. — Pyramid Lake, Nevada, is the terminus 
of the Truckee River, the only permanent stream 
entering the Pyramid Lake basin. The water level of 
the lake had become relatively stable, within recent 
geological time, balancing between inflow and 
losses from evaporation and seepage. Upstream 
development within the past century has diverted 
large amounts of water from the river with a 
concomitant decline in the water level of the lake 
and a consequent rapid increase in the concentration 
of total dissolved solids. The purpose of our project 


is to determine the effect of increasing these solids 
in the lake, on the threatened and endangered 
species — the cutthroat trout and the cui-ui. 

Project personnel are procuring and installing 
the diverse types of equipment necessary to provide 
20 closed-system units which will contain paired 
replicates of the two test species reared in five 
concentrations of water, i.e., fresh and Pyramid 
Lake water x 0.5, 1.0, 1.5, and 2.5. Concentration 
above Pyramid Lake x 1.0 will be obtained by heat- 
assisted, high-vacuum evaporation. The study will 

be continued until the test fish are sexually mature. 
Inadequate design of the lake water supply 
system has delayed the beginning of the experi- 
mental study. Correction of this deficiency, and 
completion of the evaporator-steam boiler unit 
installation will permit the study to begin. Yearling 
cutthroat trout are currently being maintained in 
the experimental units for the purpose of 
conditioning filter beds and to simulate study 
conditions, including analytical chemistry procedures 
and experimental culture techniques. 

Great Lakes Fisheries 


Registration of Lampricides for Fish. — The 

registration of chemicals used in fisheries continued 
to receive major emphasis during the year. Studies 
at the Fish Control Laboratories at La Crosse, 
Wisconsin, and Warm Springs, Georgia, were 
directed toward fulfilling requirements of the 
Environmental Protection Agency and the Food 
and Drug Administration. Many of the compounds 
now in use have never been registered or face 
reregistration deadlines in upcoming years. Data 
requirements to support applications for registration 
have risen significantly in recent years. All 
applications must now include test results to show 
that the chemicals are effective, that they have no 
lasting adverse effect on other biota, that they leave 
no harmful residues or degradation products in 
treated animals or the environment, that they are 
not carcinogenic, teratogenic, or oncogenic, and 
that they constitute no human health hazard. 

Significant progress was made during the year. A 
research protocol on the lampricide, TFM, was 
completed and an application for amended 
registration was submitted to the EPA. Data 
included with the submission demonstrate that the 
use of TFM as prescribed on the proposed new 
label is safe and efficacious for control of the sea 
lamprey in the Great Lakes. 

Work on another lampricide, Bayer 73, is nearing 
its final stages. Studies conducted in Boardman 
Lake (Michigan) indicated that although treatment 

of the Boardman River delta for larval lampreys 
resulted in a temporary depression of the numbers 
of invertebrates found in the stream bottom, the 
effect was temporary. Both the number and species 
diversity of organisms found after treatment 
indicate no lasting adverse effects. 

Laboratory tests of Bayer 73 revealed that 
selected species of snails differed widely in 
susceptibility to Bayer 73. The 96-hour LC50's were 
1.16 mg/1 for Helisoma sp. and 0.0625 mg/1 for 
Lymnaea sp. 

The freshwater prawn, Palaemonetes kadiakensis, 
was much more resistant; the 96-hour LC50 was 9.0 
mg/1. Concentrations in excess of 10.0 mg/1 
decreased the percentage of hatch in eggs of the 
leopard frog. 

Brook trout injected intraperitoneally with 0.1 
mg of Bayer 73 survived for 48 hours with no overt 
signs of toxicity. Analysis of blood and bile 
revealed a drop in calcium and a rise in magnesium 
levels in the bile-to-plasma ratios of treated fish. 

Development of methods for the analysis of 
Bayer 73 in the environment met with partial 
success. Two procedures were found for the 
determination of Bayer 73 levels in water. Both 
involve hydrolysis of Bayer 73 and color develop- 
ment of the aniline portion. There is no detectable 
interference from TFM or from phytoplankton. 
Time to complete an analysis is less than 1 hour. 
For the first time, field crews of the sea lamprey 
control program have a tool to help them 
accurately determine levels of the chemical in 


Bile collected from a trout exposed to use pattern levels of Bayer 73 will be analyzed for metabolites and residues. Photo 
by L. L. Marking. 

treated streams. 

Efforts to develop procedures for the determination 
of Bayer 73 residues in fish tissue were stymied by 
findings that residues of the chemical could not be 
separated from lipid materials in the samples. 
Although acetone extraction of fish muscle 
provided 98% recovery of 14 C-labeled Bayer 73 in 
laboratory tests, the extracts could not be analyzed 
with existing methodology because of interference 
from the naturally occurring fats. Until this 
problem is resolved, progress on residue studies is 
not possible. 

In laboratory studies conducted to improve field 
procedures for using Bayer 73, we found that little 
Bayer 73 goes into solution at pH's below 7.0. The 
amount that goes into solution is greatly reduced at 
low temperatures; about twice as much dissolves 
(per unit of time) at 12° C as at 7° C. Awareness of 
these antagonistic factors has made it possible to 

more successfully treat lamprey-containing waters 
with Bayer 73. 

Other findings included observations that the 
"fines" present in currently used formulations may 
be too small to overcome surface tension of the 
water. Data on efficacy indicate that a 1% 
formulation might increase efficacy, but that it 
would involve significantly increased costs in 
material, shipping, labor, and time. 


Restoration of Lake Trout in Lake Superior. — 

Populations of lake trout, an important commercial 
and sport species in Lake Superior, were greatly 
reduced in the 1950's due to intense exploitation 
and predation by sea lampreys. Partial control of 
the sea lamprey, protective fishery restrictions, and 


intense stocking resulted in a great increase in trout 
abundance in much of the lake by 1971. But 
populations are now the object of a large and 
expanding sport fishery in Michigan and Wisconsin, 
still threatened by continued sea lamprey predation 
throughout the lake, affected by great variation in 
annual plants of hatchery-reared fish, and 
subjected to increased commercial fishing by 
Indians in Wisconsin and Whitefish Bay, Michigan. 

Various population indices derived from 
technical data obtained annually by "contract" 
fishing, research vessel surveys, and fishery 
censuses indicate that lake trout stocks continued 
to improve in Minnesota and most of Michigan in 
1975. In Michigan, for example, fish 838-937 mm 
(33.5-37.5 inches) long tripled in abundance, and 
for the first time in 17 years of assessment fishing, a 
lake trout longer than 1,000 mm (40 inches) was 
caught. However, serious problems appear to have 
developed among stocks in Wisconsin and in 
Whitefish Bay, Michigan. In Wisconsin, abundance 
had stabilized in 1974 after three consecutive years 
of decline, only to decline again by more than 20% 
in 1975. Abundance in Wisconsin waters is 
estimated to be about half of what it was during the 
peak years of 1970-71. In Whitefish Bay, 
abundance also fell drastically — more than 70% 
from the peak in 1973. 

The abundance of spawners declined alarmingly 
since 1974 in the Apostle Islands region of 
Wisconsin — 48% on Gull Island Shoal and over 
80% at Michigan Island. The Gull Island Shoal- 
Michigan Island population is composed mainly 
(70-75%) of native lake trout and is the only 
population in southern Lake Superior that 
appeared to be self-sustaining. Apparently the 
sharp decline was caused by excessive exploitation 
in 1975. The Wisconsin Department of Natural 
Resources (WDNR) made mortality and population 
estimates of this stock by tag-and-recapture methods 
in 1974 and 1975. The commercial catch is closely 
monitored and a creel census provides data on the 
sport catch. The known catch represents a 46% 
fishing mortality on lake trout longer than 635 mm 
(25 inches). The components of this mortality consist 
of sport fishing, 13%; Indian commercial fishing, 
29%; other commercial fishing, 3%; and the 
WDNR's assessment fishing and egg-taking 
operations, 2%. 

Although these specific declines are alarming, the 
overall lake trout picture exhibits some encouraging 
trends. Among cohorts of lake trout planted at 
various times over the last 15 years further east in 
Keweenaw Bay and in the Marquette-Munising 

area, the total annual mortality between ages IX 
and XIII has declined sharply. Annual mortality of 
lake trout between ages VI and IX was on the order 
of 0.65 to 0.80 during the late 1960's, when 
mortality beyond age IX averaged almost 100%and 
few females reached maturity. In the past 6 to 8 
years, total mortality has fallen to about half the 
1966-68 level, and relatively strong spawning 
populations have developed at several locations. 
The estimated sport, commercial, and incidental 
catch of lake trout in Michigan waters now 
approximates half the historic commercial catch 
before the great decline of the 1950's. 

Furthermore, the incidence of fresh sea lamprey 
wounds in the spring of 1975 remained near the low 
1974 levels on all sizes of lake trout. Since 1964, the 
wounding rate for 17- to 20-inch fish has changed 
little. However, wounding on 21- to 24-inch fish 
declined about 35%, that on 25- to 28-inch fish 
about 47%, and that on 29-inch and larger fish, 
about 55% over the same period. These trends 
probably reflect substantial changes in the 
predator-prey ratios that have been altered more by 
increases in abundance of the larger trout than by 
decreases in abundance of sea lampreys. 

Decline of Lake Superior Herring Stocks. — 
Landings of lake herring in U.S. waters of Lake 
Superior declined from a peak of 17.8 million 
pounds in 1941 to only 314,000 pounds in 1975. 
Landings in Canadian waters still exceeded the 
1941 catch there of 1.4 million pounds. Although 
overfishing is suspected as the major cause of 
decline of herring stocks, predation on, and 
competition with, the larvae by rainbow smelt have 
also been widely proposed as possible causative 

During fiscal year 1976, examination of all 
commercial fishing records from Wisconsin waters 
of Lake Superior from 1940 to 1961 was completed, 
along with the extraction of all lake herring catch 
and effort statistics. Fishing localities were 
identified by statistical grid. 

Preliminary analyses point toward the sequential 
"fishing-up" of individual (local) populations as 
having been primarily responsible for the historic 
declines in lake herring. For example, during the 
decade 1950-59, the total harvest from Wisconsin 
waters averaged 4,290,000 pounds per year, of 
which 98% was taken in bottom-set gill nets during 
the fall spawning season. About 60% of the fish 
produced were taken in two relatively small 
Wisconsin bays: Siskiwit Bay near Cornucopia 
(880,000 pounds) and Big Bay on Madeline Island 
(1,690,000 pounds). During this decade, total effort 


in these two bays nearly doubled while the catch 
declined — from about 3,430,000 pounds in 1950- 
52 to about 980,000 pounds in 1957-59. The next 
phase of our study will deal with biomass estimates 
and yield projections as guides to future manage- 
ment of this species. 

The possibilities of significant smelt predation 
on, or competition with, larval lake herring were 
studied during 1974-75 in a cooperative program 
between the Service's Ashland Biological Station 
and the Ontario Ministry of Natural Resources at 
Thunder Bay. Most sampling was done during May 
and July in Black Bay, Ontario, and in the lake 
proper among the Apostle Islands, Wisconsin. The 
herring in Black Bay are still abundant and 
annually yield about 1.5 million pounds, whereas in 
the Apostle Islands they are sparse and declining in 
number. Smelt are about equally abundant in the 
two areas. 

In examining the question of competition, we 
observed that lake herring began feeding shortly 
after hatching — all or nearly all before the yolk sac 
was fully absorbed — and that their food was 
similar in the two sampling areas: mainly copepod 
nauplii at first, then larger copepods as the herring 
grew. Smelt eggs hatched inshore, and much later in 
the year than herring eggs; thus larvae of the two 
species did not cohabit the area studied and could 
not have competed for food. Although juvenile 
(age I) and adult (age II and older) smelt occupy the 
same areas as herring larvae, they eat different 
invertebrate species (or life stages thereof) than do 
herring larvae and therefore do not compete 
directly for food. The species composition of the 
zooplankton showed no evidence that it had been 
altered through selective feeding by smelt in any 
way that would be harmful to herring larvae. 

To evaluate predation, we examined stomachs 
from a total of 1,195 Black Bay smelt, of which 685 
(57%) contained food. Of the 685 smelt with food, 
204 (30%) contained one or more herring larvae. 
We also examined the stomachs of 1,711 Apostle 
Islands smelt, of which 1,146 (67%) contained food 
but no herring larvae. Predation on herring by 
smelt, as observed in spring 1974, is probably not 
high enough to be a matter of concern, especially 
since the herring population of Black Bay appears 
to be relatively stable. The total number of herring 
larvae migrating out of the bay is probably 
sufficient to maintain the fish population in the 
open lake. We believe that predation in the open 
lake, as in Wisconsin waters, is low or nonexistent. 
Our failure to detect any predation in Wisconsin 
suggests that smelt predation plays no role in the 

continuing decline of the herring population in the 
open waters of southwestern Lake Superior. 

Update on Morphology of Lake Superior 
Coregonines. — The systematics of Lake Superior 
ciscoes have perplexed field biologists for years. 
But today, with stocks of some species greatly 
diminished, there is a critical need for a more 
reliable field method for distinguishing the forms so 
they can be adequately protected and the fishery 
properly regulated. During 1975-76, we clarified 
the relationships between these ciscoes by using 
modern analytical techniques such as cluster- 
analysis, principal-components, and discriminant- 

For Coregonus nigripinnis cyanopterus, C. 
reighardi dymondi, and C. zenithicus, a total of 27 
meristic and morphometric characters were 
measured, including gillraker number, fin lengths, 
fin rays, jaw lengths, snout length, and eye 
diameter. All study specimens were from collections 
in the University of Michigan Museum of Zoology 
made by Walter Koelz for his 1929 monograph, The 
Coregonid Fishes of the Great Lakes. 

Principal-components analyses demonstrated 
that the C. nigripinnis cyanopterus were merely 
large specimens of C. zenithicus. Slight differences 
in body proportions associated with large size were 
the only discriminating features of C. nigripinnis 

In contrast, C. reighardi dymondi was recogniz- 
ably distinct from C. zenithicus. The geographic 
distributions of the two forms overlapped, and 
principal-components analyses showed that C. 
reighardi dymondi was less similar to C. zenithicus 
populations within the area of overlap than to 
populations outside it. This character displacement 
further suggested that these two forms were 
distinct. C. reighardi dymondi was restricted to the 
large bays and immediately adjacent waters of 
northwestern Lake Superior, but included Lake 
Nipigon, Ontario. C. zenithicus -was found 
throughout Lake Superior, but we believe that 
records of its occurrence in Lake Nipigon were due 
to misidentification. 

Condition and Management of Lake Michigan 
Chubs. — The bloater is the last commonly 
occurring representative in Lake Michigan of an 
original group of seven deepwater ciscoes or 
"chubs," important coregonines that once sustained 
a sizable commercial fishery and provided a forage 
base for lake trout. Smallest of the seven species, it 
has represented more than 99% of the fishable chub 
stock since the early 1960's. Chubs declined 
drastically in abundance in the 1960's and early 


Gill net sampling of bloater chub stocks in Lake Michigan. This species has seriously declined in abundance since the 
mid-1960's and a lakewide moratorium on commercial fishing has recently been imposed. Photo by R. M. Julian. 

1970's — possibly because of competition from 
alewives and smelt and (more recently) depletion of 
spawning stocks through exploitation. 

Comprehensive surveys by the Fish and Wildlife 
Service in 1974 revealed that chub abundance was 
but a small fraction of what it had been in 1960 and 
1961 — down to less than 1% in western and 
northern Lake Michigan. Results of similar surveys 
in 1975 showed little or no improvement in the 
depleted chub stock, despite temporary bans on 
fishing in 1975 as the states sought legislative and 
judicial means for permanently closing the chub 
fishery. To slow down declining recruitment and 
foster possible rebuilding of the resource, the Great 

Lakes Fishery Commission's Chub Technical 
Committee, which is composed of Service and State 
biologists, recommended such closure in 1974. 
Preliminary results of special sampling with gill 
nets and trawls in June 1976 suggested that, 
although chub populations in southern Lake 
Michigan are still only a fragment (1 to 5%) of what 
they were in 1960, the downward trend may have 
been at least temporarily halted in some areas by 
improved recruitment from one or two recent year 

State efforts during 1975 and 1976 to ban fishing 
on the severely depressed chub population were 
challenged repeatedly in the courts by the fishing 


industry, and only by late summer of 1976 did it 
appear they would be successful. 

Lake Michigan Alewife Stock in Healthy 
Condition. — During the Laboratory's resource 
surveys with experimental trawls in fall 1974, body- 
weight indices, which reflect the general physical 
condition of adult alewives, fell to the lowest levels 
recorded for Lake Michigan since the huge 
population buildup that preceded the massive die- 
off in 1967. Because poor physical condition limits 
the ability of alewives to withstand temperature 
stresses in winter and early spring, we predicted that 
a heavier die-off than in recent years might occur in 
1975. Moderately heavy concentrations of dead 
alewives were later seen from research vessels along 
the east shore of the lake in spring 1975. A 
commercial fisherman in the Frankfort, Michigan, 
area also reported in late June that the die-off there 
was the largest he had seen in several years. By fall 
1975, the physical condition of the adults had 
improved throughout the lake, and we predicted 
that die-offs in the spring of 1976 would be 
relatively light. Observations from various Federal 
and State research vessels during the spring of 1976 
substantiated this prediction. 

Despite considerable year-to-year variation, 
alewife samples taken by bottom trawls at 
permanent index stations throughout the lake, and 
the temporarily poor physical condition of alewives 
generally in 1974, the stock itself continues to 
appear to be stabilized at a substantially high level. 
The average catch per unit of sampling effort (CPE) 
for adults at four index stations in southern Lake 
Michigan (410 fish per 10-minute trawl tow) in fall 
1975 was the highest recorded since 1967. This high 
rate was mainly attributable to record catches off 
Benton Harbor (555 fish per tow) and Waukegan 
(861 fish). The combined CPE for young-of-the- 
year was down somewhat from 1974 but was still 
the third highest of the 9-year survey period. Lake- 
wide, adult alewives appeared to be more abundant 
in 1 975 than in 1 974, whereas the young were less so 
— although they were by no means scarce. 

Assessment of Lake Michigan Lake Trout. — 
Lake trout supported the most valuable commercial 
fishery in Lake Michigan for nearly half a century. 
In the mid-1940's, however, the species began a 
decline that led to its extinction there by 1956, 
chiefly due to mortality imposed by the sea 
lamprey. Present efforts to rehabilitate the lake 
trout involve both sea lamprey control and the 
stocking of hatchery-reared fish, both of which are 
administered by the Service through the Great 
Lakes Fishery Commission. Good survival has 

permitted lake trout to become abundant again, 
although they have not yet reproduced naturally in 
Lake Michigan. Fishery managers must have 
continuous information on the distribution, 
abundance, and vital statistics of the lake trout 
stock to restore it to self-sustainability and 
maximum productivity, to guage its performance in 
response to exploitation, and to project its annual 
surplus production for allocation among the 
various users. 

Samples of Lake Michigan lake trout for data on 
abundance and age distribution, and on the 
incidence of sea lamprey wounds, were collected 
again in late 1975 off Saugatuck for the fifth 
consecutive year. The collections included 890 lake 
trout planted lakewide as yearlings in the springs of 
1967-75; 11 stocked off Ludington, Michigan, as 
fingerlings in the fall of 1967; 57 released off Grand 
Haven, Michigan, as fingerlings in the falls of 1971- 
74; and 13 for which the origin could not be 
determined. Not represented in the catches were 
fish planted in spring 1965 and 1966, which 
unquestionably have become very scarce. 

As indicated by the number of fish caught per 
unit of sampling effort, the overall abundance of 
lake trout off Saugatuck did not appear to be 
greatly different in 1975 than in several previous 
years. The average weight offish in 1975 was 2.9 kg, 
as compared with 2.4 kg in 1974. Sea lamprey 
wounding rates in 1975 climbed moderately, but 
not alarmingly, from the extremely low levels of 
1974. The 1975 rates were 3.4, 1.5, and 3.6% for fish 
in the 533- to 634-mm, 635- to 735-mm, and 736- to 
837-mm length classes, respectively. Rates in 1974 
were less than 1% in all length categories. 

Laboratory staff members joined State personnel 
in the first meeting of another technical working 
group organized by the Great Lakes Fishery 
Commission, this one addressing the problem of 
interagency assessment and management of 
fisheries for lake trout in Lake Michigan. The 
group's long-range goal is to develop the strategy 
for a unified, interagency program of lake trout 
assessment that will provide a scientific data base 
for possible management (on a lakewide basis) of 
the stock and the fishery it supports. Now under 
way is a multiagency effort to assemble and begin 
analysis of all available data on the fisheries, 
biology, and dynamics of the lake's past and present 
lake trout resource. 

Status of Lake Michigan Yellow Perch. — 
Yellow perch populations throughout Lake 
Michigan have changed greatly in recent years, as 
evidenced by assessment surveys as well as by 


commercial and sport catches. In the early 1960's, 
high commercial production, together with high 
catch per unit of effort, was followed by an abrupt 
decline. The sequence occurred somewhat earlier in 
northern than in southern reaches of the species' 
primary range in Lake Michigan. A nearshore sport 
fishery, conducted mostly from breakwalls in the 
lake proper and from boats in Green Bay, collapsed 
a few years earlier than the commercial fishery. 
Fortunately, this decline has apparently reversed, 
and catches by the commercial fishery (in waters 
where it is still allowed to operate) and the sport 
fishery have partly recovered in the 1970's. 
Commercial fishing for perch is now banned in 
Michigan but allowed in other states. However, the 
Michigan Department of Natural Resources is 
considering the long-range possibility of a limited- 
entry commercial fishery for perch with entrapment 
gear, consistent with protection and sustained 
productivity of the stocks. 

As revealed by our annual systematic sampling in 
1975 around the perimeter of Lake Michigan, 
yellow perch continue to be most abundant in the 
southeastern sector of the lake. Their persistent 
scarcity along the western shore suggests that a 
recovery of perch stock there, similar to that which 
occurred along the eastern shore several years ago, 
will not take place in the foreseeable future. 

Forage-fish Stocks in Lake Huron. — Success of 
the intensive program by United States and 
Canadian fishery managers to reestablish self- 
sustaining lake trout populations and introduce 
Pacific and Atlantic salmons, splake, and other 
salmonids in Lake Huron relies heavily on the 
adequacy of the forage base to support large 
populations of predator species. Information on 
the size and composition of the forage base, 
primarily alewives and rainbow smelt, must be 
accurate and timely if it is to be used effectively by 
fishery managers. Survey and biostatistical data 
must be developed for use in computation of 
standing stock, turnover rates, and surplus 
production of the forage fish. 

Systematic sampling with mid-water and bottom 
trawls at permanent index stations off Hammond 
Bay, Alpena, Harbor Beach, and AuSable Point 
during 1975 provided the third year of base-line 
data on the distribution, abundance, and biology of 
alewives and smelt. Alewife abundance increased 
during 1975 for the second consecutive year; catch 
of adult fish per unit of effort was 50% greater than 
in 1974. Smelt abundance was essentially the same 
in 1975 as in 1974 but appeared to have increased 
somewhat in the spring of 1976. 

Catches of young-of-the-year alewives during fall 
surveys are closely correlated with catches of 
yearlings the following spring. This fact and 
collaborative age and growth data suggest that the 
fall catch of young-of-the-year represents an early 
and reliable indicator of relative year-class 
strength. Our predicted catch of alewives per unit of 
effort in the spring of 1976 was within 0.5% of the 
actual catch. 

Estimates of the standing stocks of alewives and 
smelt were derived from average densities of each 
species by combining mid-water and bottom 
components of the populations and expanding such 
densities by depth-contour intervals to encompass 
all U.S. waters of Lake Huron. The standing stocks 
in the fall of 1975 were estimated at 31,000 metric 
tons of alewives and 18,500 metric tons of smelt. 
Continued refinements of our estimates and their 
integration with analyses of age and growth will 
improve our ability to accurately project standing 
stocks of forage fishes. 

Status and Management of Lake Erie Walleyes 
and Yellow Perch. — Surveys during 1975 
indicated that the walleye population in Lake Erie's 
western basin is probably the largest it has been 
since the mid- 1950's. Moreover, the age structure of 
the population appears to be stabilizing, with many 
year classes and older age groups well represented. 
This resurgence may be attributed to restraints on 
commercial fishing since 1970 and to the 
production of relatively strong year classes in 1970, 
1972, and 1974. 

In contrast, the population of walleyes in eastern 
Lake Erie appears to have weakened. Samples of 
commercially caught walleyes showed the presence 
of only one strong year class (1971), which made up 
the bulk of both spring and fall landings. As this 
year class disappears, without sufficient replacement, 
the take of walleyes from the eastern basin is 
expected to decline significantly in 1976. 

Yellow perch populations continued to deteriorate 
in 1975, especially in the western basin. The lake- 
wide commercial catch of 9.9 million pounds was 
the lowest recorded since 1966 and, before that, 
1955. In addition, the 1972-74 year classes are 
comparatively weak and are not expected to make 
significant contributions. The 1975 year class, as 
indicated by data from the Ohio Department of 
Natural Resources, was somewhat stronger and 
may become the mainstay of commercial production 
during 1978-79. 

The Scientific Protocol Committee on Interagency 
Management of the Walleye Resource of Western 
Lake Erie, sponsored by the Great Lakes Fishery 


Commission, presented its First Technical Report 
to the Commission's Lake Erie Committee in mid- 
June 1976. In brief, the report described the 
Protocol Committee's procedure in developing a 
technical basis for managing the walleye fishery by 
means of catch quotas for each regulatory agency. 
Among other considerations, the Protocol 
Committee (1) determined that the moratorium on 
commercial fishing imposed in 1969, together with 
highly favorable spawning conditions in several 
intervening years, has permitted the stock to 
recover rapidly; (2) projected the 1976 standing 
stock of catchable-size walleyes at almost 9 million 
fish; (3) forecast the stock's expected surplus 
production at slightly over 900,000 fish weighing 
about 1.6 million pounds; and (4) recommended 
catch quotas of 80,500 walleyes for Michigan, 
335,000 for Ontario, and 479,500 for Ohio. Follow- 
up recommendations for 1977 are in preparation. 

A technical committee to develop the scientific 
rationale for adjusting the minimum commercial 
size limit for yellow perch in western Lake Erie was 
appointed at the Lake Erie Committee meeting of 
the Great Lakes Fishery Commission in March 
1975. This committee, composed of representatives 
from Ohio, Ontario, and the U.S. Fish and Wildlife 
Service, submitted its report to the Lake Erie 
Committee in January 1976. The report concluded 
that under heavy exploitation, with the present 
minimum length limit of 8 inches, and in the 
absence of any strong year classes produced since 
1965, the yellow perch resource of western Lake 
Erie has severely deteriorated in recent years. The 
Committee recommended an increase in the 
minimum length limit to 8'/2 or 8% inches and urged 
a firm commitment from all agencies to strictly 
enforce any new limit imposed. 

Effects of Egg Predation and Environmental 
Factors on Production of Walleyes in Western 
Lake Erie. — In a previous study, marked annual 
differences in year-class success ( 1 960-70) could not 
be correlated with differences in brood stock size. 
However, the rate and regularity of water warming 
during the spring spawning and incubation periods 
were shown to be strongly correlated with the 
density of egg deposition and resulting year-class 
strength. Although slower-than-average rates of 
warming were not themselves detrimental, low 
temperatures extended the length of the incubation 
period, which in turn increased egg exposure to 
such negative influences as dislodgment from 
spawning reefs by strong currents, siltation, and 
low dissolved oxygen. It is hoped that the recovery 
of the walleye brood stock during the past several 

years, and the expected increased egg deposition in 
a greater number of spawning locations during 
years with adverse environmental conditions, will 
help insure at least a fair hatch and year class. 
Evidence suggests that this happened in 1975. 

In another study published during the year, 
examination of stomachs from 21 species of fish 
captured over a walleye spawning reef in western 
Lake Erie disclosed that spent yellow perch were 
the most consistent predators on walleye eggs. Yet, 
never in 3 years of observation were spent yellow 
perch abundant enough on the walleye reefs to 
impose serious mortality on walleye eggs. Only 
under the very uncommon condition of an 
extended time overlap between walleye egg 
hatching and perch spawning, resulting in the 
presence of large numbers of actively feeding spent 
perch, could egg predation reduce walleye 
reproductive success. 

Development of a Chemosterilant for Sea 
Lamprey. — The sea lamprey is now being 
controlled with chemicals at a level corresponding 
to about 10-20% of its peak abundance in the late 
1950's. The chemical control program that 
selectively destroys the stream-dwelling larvae is 
very costly, however, and further reduction in 
lamprey abundance by this means would be 
prohibitively expensive. Consequently, the Great 
Lake Fishery Commission has established the long- 
range goal of developing an integrated control 
program that will include the continued application 
of selective larvicides where appropriate, as well as 
any other methods that may prove effective in 
attaining the desired level of control. One of the new 
sea lamprey control methods now being developed 
and evaluated by the Great Lakes Fishery Labora- 
tory, under contract with the Great Lakes Fishery 
Commission, involves the release of artificially 
sterilized, sexually mature lampreys into streams 
containing spawning populations of lampreys. In 
principle, these sterile individuals will compete 
successfully with fertile ones for mates and thereby 
reduce the reproductive success of the spawning 
population. Search for a chemosterilant that would 
permit testing of the sterile-lamprey release 
technique was initiated at the Laboratory's 
Hammond Bay Biological Station in 1971. Tests at 
the Station showed that P,P-Bis (l-aziridinyl)-TV- 
methylphosphinothioic amide ("PMPA") dis- 
solved in saline and injected intraperitoneally at a 
dosage of 100 mg/kg sterilizes spawning run sea 
lampreys. Field tests conducted in 1974 on an 
experimental population of spawning adults 
established in an isolated portion of the Big Garlic 


River, Marquette County, Michigan, confirmed 
that treatment of male sea lampreys with PMPA 
sterilized them; these field studies also showed that 
PMPA treatment had no apparent effect on the 
nest-building activity, spawning behavior, or 
mating competitiveness of the sterilized lampreys. 

A second field study was conducted in the Big 
Garlic River in 1976 to provide a quantitative 
demonstration of the effectiveness of the technique. 
On June 5, 1976, a total of 270 PMPA-sterilized 
male sea lampreys, together with 30 normal males 
and 70 females, were released in the study area. 
Spawning began on June 20 and continued through 
July 6. The study area was surveyed daily, and a 
total of 213 lamprey nests were found. A case 
history was kept of the lamprey activity at each nest 
through July 6. On July 6-8, all 213 nests were 
sampled to determine if they contained eggs or 
embryos and to ascertain the stage of development 
of those present. Seventy-four nests containing live 
eggs or embryos were found; each of these nests was 
then completely excavated and the contents were 
washed into a fine-mesh plankton net and 
preserved for analysis. Preliminary analysis of these 
preserved samples indicates that viable offspring 
were produced only in nests where normal males 
spawned with normal females. In nests where sterile 
males spawned with normal females, embryos 
developed through the early stages and then died. 
The available information suggests that a 
quantitative demonstration of the effectiveness of 
the sterile-male lamprey release technique will be 
possible when analysis of the preserved samples is 

Benthos Populations as Indicators of Habitat 
Quality. — The St. Marys River, connecting Lakes 
Superior and Huron, is a heavily traveled shipping 
route and is also the recipient of municipal and 
industrial wastes of two cities. River populations of 
warm- and cold-water fishes support an important 
sport fishery. Many of these fish feed extensively on 
the benthic invertebrate fauna, the more important 
of which are mayfly nymphs and caddis fly larvae. 
Urban and industrial growth, as well as an extended 
shipping season, represent possible threats to the 
quality and abundance of the river's macrobenthic 
invertebrate fauna. 

Limited sampling by the Great Lakes Fishery 
Laboratory in 1971-73 indicated that populations 
of mayfly nymphs and caddis fly larvae were 
abundant in many parts of the St. Marys river, 
except those polluted by industrial wastes; it failed, 
however, to provide a comprehensive description of 
the distribution and abundance of these organisms 

in this important river system. During May 1974 to 
May 1975 we expanded our sampling coverage and 
collected a total of 580 benthos samples from 167 
stations throughout the river system downstream 
from Sault Ste. Marie. Analysis of about 70% of 
these samples confirmed that burrowing mayfly 
nymphs (mostly Hexagenia and Ephemera) and 
caddis fly larvae (mostly Phylocentropus, Poly- 
centropus, Oecetis, Mystacides, and Triaenodes) 
were indeed present in substantial numbers 
throughout the river system, except in the North 
Channel of the river from Sault Ste. Marie 
downstream for a distance of about 15 miles. In that 
portion of the river, oil was visible on the surface of 
the water and in the bottom samples, and none of 
the samples contained mayfly nymphs or caddis fly 
larvae. Analysis of the remaining samples will 
permit us to describe more precisely the downstream 
extent of the heavily polluted area. 

Biological Effects of Heated-water Release for 
Ice Suppression in Navigation Channels. — The 
U.S. Army Corps of Engineers conducted a small- 
scale test in January- April 1976 to determine the 
feasibility of using waste heat from a steam-electric 
power plant to reduce ice cover in a shipping 
channel. The test site selected was about 1 mile off 
the mouth of the Saginaw River in lower Saginaw 
Bay, Lake Huron. Heated water from the Karn- 
Weadock power plant discharge canal was pumped 
through a submerged 800-foot diffuser pipe 
positioned along the edge of the navigation 

To provide a basis for evaluating the effects of the 
heated-water release on the important biota at the 
test site, the Great Lakes Fishery Laboratory 
conducted a study funded by the Corps, from 
November 1972 to May 1976. Benthic invertebrates 
were sampled before and after the test with a Ponar 
grab. The fish population at the test site was 
sampled before, during, and after the release of 
heated water. Gill nets, trawls, and small (2x2x4 
feet) nardware-cloth funnel traps were used when 
the site was ice free; when there was ice cover, only 
the funnel traps were used. 

Pollution-tolerant oligochaetes and midge larvae 
were the principal benthic organisms present in the 
samples. No changes in the abundance of these 
dominant organisms that could be attributed to the 
release of heated water at the test site were 
observed. Most of the observed differences in the 
kinds and numbers of benthic invertebrates 
throughout the study area appeared to be related to 
differences in substrate type. Preliminary evaluation 
of the fish-sampling data also failed to reveal any 


major changes in the kinds and numbers offish in 
the test area that could be attributed directly to the 
release of heated water. Large changes were 
observed in the fish population on several 
occasions, but these were accompanied by strong 
currents and high turbidity and appeared to be 
related to the volume of discharge from the 
Saginaw River. 

The absence of observable effects of the release of 
heated water on benthic invertebrates and fish at 
the test site is not surprising because the test was of 
short duration, the release of heated water was 
intermittent, the maximum excess temperature 
measured in the test area was never more than 1° C, 
and the Corps apparently avoided pumping 
chlorinated water to the test site. In addition, the 
influence of the polluted Saginaw River discharge 
on the test site probably tended to preclude 
detection of any subtle effect of the heated water on 
fish and benthos. 

Effects of Food Availability and Temperature on 
Food Competition Between Young-of-the-year 
Perch and Alewives. — The effects of small 
temperature increases on fish and other aquatic 
organisms that inhabit littoral waters receiving 
waste heat from power-generating plants have not 
been measured. Information developed at the Great 
Lakes Fishery Laboratory and elsewhere suggests, 
however, that even small increases in water tempera- 
ture, especially during the warmer months of the 
year, create locally undesirable conditions for 
some native fauna. Under the hypothesis that the 
functional efficiency of some species may be so 
impaired by elevated temperature as to cause them 
to desert the affected portion of their range or suffer 
reduced survival, the Laboratory is conducting 
controlled experiments to observe the effects of 
temperature increases on the availability of food to, 
and competition for food among, prey and 
predator species. 

More specifically, these studies, being made at 
the Laboratory's Hammond Bay Biological 
Station, are to determine the effect of food 
availability and ambient temperature on the 
feeding rate, food selectivity, growth, and survival 
of mixed- and single-species populations of young- 
of-the-year alewives and yellow perch. The young 
yellow perch and alewives are being used because 
they have similar optimum temperatures, are 
planktivorous, and occupy the same habitat. 
Moreover, the abundance of perch and alewives, in 
Lake Michigan for example, also appears to vary 
inversely, suggesting a significant degree of 
competition between the two species in that lake. 

In our early tests, single-species populations of 
young-of-the-year perch and alewives (total of 480 
fish of each species) were acclimated to 10°, 15°, 
20°, and 25° C, and fed mixed zooplankton that 
included Daphnia magna, D. pulex, Bosmina 
longirostris, and small copepods at a level of 0.5, 
1.0, 2.5, or 5.0% of their body weight. Examination 
of stomachs from perch acclimated to 25° C 
indicated that they preferred the largest zoo- 
plankter, D. magna, to the smaller plankters, 
despite the greater abundance of the smaller 
plankters in the food mixture. However, the perch 
acclimated to 10° C were relatively inactive and 
unselective feeders with regard to size and species of 
prey organisms. Forty-six percent of the food 
ingested by perch acclimated to 10°C consisted of 
the small prey organisms, Bosmina and copepods, 
whereas these smaller plankters made up only 3% of 
the stomach contents of perch acclimated to 25° C. 

Analysis of 50 of the 480 preserved alewife 
stomachs indicated that alewives fed more 
extensively on smaller plankters than did young 
perch — suggesting that the alewives may have a 
competitive advantage over perch when the food 
supply consists primarily of organisms smaller than 
D. pulex. 

Effect of Sublethal Heat Shock on Great Lakes 
Zooplankton. — Relatively large quantities of 
zooplankton inhabiting nearshore waters of the 
Great Lakes pass through power plant cooling 
systems. Available information indicates that 
about 7% of entrained zooplankton is killed by 
mechanical damage and heat stress. Little is known 
of the effect on the remaining 93% of the entrained 
population that apparently survives, although one 
suspected effect of heat stress on zooplankton is a 
reduction in reproductive potential due to a 
lengthening of the time between generations. 

To determine experimentally if the reproductive 
potential of zooplankton populations is reduced by 
sublethal heat shock, we acclimated laboratory 
populations of typical zooplankters, Daphnia 
magna and D. pulex, to 10°, 15°, 20°, or 25° C; 
exposed them suddenly to temperatures 10°, 15°, 
or 20° C above their acclimation temperature for 2 
minutes; and then cooled them quickly to their 
previous acclimation temperature. Shock tempera- 
tures and the postshock cooling rate were selected 
to approximate those that would be experienced by 
a plankter during passage through the cooling 
system and discharge plume of a large nuclear- 
fueled power plant on the Great Lakes. We 
monitored test and unshocked control populations 
after 9, 18, and 27 days (or until the density of 


organisms in a test chamber limited population 
growth) and recorded numbers of individuals, their 
relative sizes, number of eggs per female, and 
production of ephippia (capsules containing winter 

Exposure to shock temperatures 15° and 20° C 
above the acclimation temperature was lethal for 
D. magna and D. pulex acclimated at 25° C. At 
lower, nonlethal shock and acclimation temperature 
combinations, heat-shocked populations of both 
species were usually smaller than control populations. 
The difference between heat-shocked and control 
populations of D. magna acclimated at 10°-25°C 
became apparent 9 days after heat shock; for D. 
pulex the difference became apparent after 12, 18, 
and 22 days for groups acclimated at 10° , 15° , and 
20° C, respectively, and shocked at temperatures 
10°-20°C above the acclimation temperature. D. 
pulex acclimated at 25° C and shocked at 10°C 
responded by increasing the production of 
ephippia. These results suggest that D. pulex has a 
longer generation time than D. magna and thus 
would be more adversely affected than D. magna by 
sublethal heat shock received during entrainment. 

Nutrient Cycling and Plankton Productivity in 
the Nearshore Waters of Lake Huron. — Intensive 
limnological studies were conducted from 1973 to 
1976 in the nearshore waters and tributary streams 
of northwestern Lake Huron near the Hammond 
Bay Biological Station to examine the relationships 
between seasonal changes in nutrient availability 
and plankton abundance, and to determine the 
influence of atmospheric fallout and land runoff on 
the nutrient dynamics of the nearshore waters. 
Knowledge of nutrient-plankton dynamics in this 
portion of Lake Huron, which appears to be 
relatively undisturbed by man's activities, will 
provide a basis for interpreting changes observed in 
other parts of the Great Lakes that have been 
heavily affected by man. 

Sampling in the nearshore waters of the 
Hammond Bay ecosystem (1973 to 1975) revealed 
that phosphorus concentrations were consistently 
low throughout the year (<10/ig/l), suggesting that 
primary productivity in these waters, like that in 
other unpolluted portions of the Great Lakes, is 
phosphorus limited. Concentrations of nitrate and 
silica, two other nutrients known to regulate 
plankton productivity, were highest in the spring 
(280 and 2,500 mg/1, respectively) and lowest 
during the summer ( 1 50 and 600 mg/ 1, respectively). 
Data obtained weekly (July 1975- June 1976) by 
sampling six streams entering Hammond Bay 
indicate that high nitrate and silica concentrations 

in tributary runoff during February and March 
contribute significantly to the high spring 
concentrations of nitrate and silica in nearshore 
Hammond Bay waters. 

Examination of phytoplankton in samples 
collected from the nearshore waters of Hammond 
Bay (March 1973-July 1975) has shown that 
diatoms (largely Tabellaria fenestrata) were the 
most abundant group numerically and volumetri- 
cally during the spring of 1973; other taxa made up 
less than 5% of the total number and volume. 
Maximum density of algal cells observed thus far 
was only 234/ ml, which is considerably below the 
average densities of 1,000 to 4,000/ ml reported by 
other investigators for open Lake Huron and 
Saginaw Bay in southwest Lake Huron, respectively. 
These results support our hypothesis that the 
nearshore waters of Hammond Bay are indeed 

Crustacean zooplankton in samples collected 5 
days per week from June 1973 to July 1975 in 
Hammond Bay have now been identified and 
counted. Computer plots of geometric mean 
densities of various taxa and total zooplankton by 
day, week, and month reveal that zooplankton 
density was highest in midsummer (2.4 per liter) 
and lowest in late winter and early spring (0. 1 per 
liter), as has been reported in the literature for the 
open waters of Lake Huron and for Georgian Bay 
in northeast Lake Huron. 

All of the results obtained thus far are consistent 
with the expected nutrient-plankton relations in an 
unpolluted portion of the Great lakes. 

Forage Requirements of Lake Trout and Coho 
Salmon. — Work continues on the development of 
information required in formulating energy 
budgets for salmonids in Lake Michigan. These 
budgets, when completed, will permit the prediction 
of forage needs in relation to the capacity of the 
lake's forage base to support growing salmonid 

The energy necessary for the routine metabolic 
activity of lake trout was determined by measuring 
the oxygen consumption of 503 lake trout ( 1 74 tests 
with 1, 3, or 20 fish) forced to swim in a tunnel 
respirometer at various controlled speeds (10 to 60 
cm per second) and temperatures (3.5° to 18.0° C). 
The oxygen consumed by these fish was converted 
to caloric equivalents by incorporating a standard 
oxycalorific coefficient into the energy budget. 

Linear regressions describing the relation 
between the logarithm of oxygen consumption and 
swimming speed have been computed for each of 
the five temperatures tested. The standard 


metabolic rates or resting metabolic rates were 
estimated by extrapolating the regression lines to 
the point of zero activity (swimming speed zero). 
Since these extrapolations require only a short 
extension of the regression lines to the Y-intercept, 
the estimated rates give a reasonably good 
approximation of the maintenance oxygen require- 
ments of the fish. The logarithm of the rates increases 
linearly with temperature from a low of 39 mg/kg 
per hour at 3.5° C to a high of 1 29 mg/ kg per hour at 
18° C, or about a threefold increase. The relations 
between rate of oxygen consumption and fish 
weight, activity level, and temperature were 
described by a multiple regression equation, and 
the equation can be used to predict either the 
oxygen or caloric requirements of lake trout 
whenever their weight, swimming speed, and 
ambient temperature are known. 

Effects of Temperature on Sperm Quality in 
Great Lakes Fishes. — Attraction of fish to heated 
waters from power plants has long been considered 
potentially detrimental to the normal life cycle of 
fish. Although considerable research has been done 
to show how temperature affects the rate of 
development and hatchability of fish eggs, little is 
known about the temperature requirements of fish 
sperm and the effects of temperature alteration on 
their viability and mobility. 

Major problems in performing studies with 
sperm of coldwater fishes are the lack of adequate 
experimental techniques and the short and 
infrequent periods in which viable sperm may be 
observed. To assist in the development of improved 
techniques for testing sperm viability, we have been 
using the flagfish {Jordanella floridae) — a 
warmwater species that matures in 6 to 8 weeks 
after hatching and spawns continuously throughout 
the year — as a source of viable sperm. 

As part of preliminary testing, it was necessary to 
establish the thermal tolerance of flagfish. Using 
previously described techniques, we determined 
that flagfish have an ultimate upper lethal 
temperature of 39.7° C and a broad range of 
thermal tolerance. 


Alternate Souces of Biotin for Lake Trout. — In a 

study designed to determine the suitability of corn 
distillers solubles (CDS) as a biotin source for 

trout, growth of trout fed CDS (compared with 
those fed crystalline biotin), and the microbiological 
assays for dietary biotin, showed that the dietary 
CDS contained much less biotin than published 
values indicate, and that it appears to be a poor 
source of this vitamin. The testing of other 
feedstuffs for biotin is needed. The results also 
confirmed earlier indications that lake trout need 
no more than 0. 1 ppm dietary biotin. This level is 
well below the recommendation of the 1973 
National Research Council for optimum growth 
and feed utilization of salmonids. 

Dietary Interrelations of Biotin and Pantothenic 
Acid in Lake Trout: New Deficiency Signs. — 
Results of a feeding study, conducted to further 
characterize dietary biotin and pantothenate 
deficiency signs in lake trout, showed heretofore 
unreported symptoms in addition to the deficiency 
signs classically associated with the feeding of diets 
lacking these two vitamins. A simultaneous 
deficiency of both biotin and pantothenate caused a 
slower growth rate, more severe anemia and 
atrophy of acinar (enzyme-producing) pancreatic 
cells, and a higher death rate than occurred in trout 
fed a diet deficient in either biotin or pantothenate 
alone. The simultaneous lack of dietary pantothenate 
and biotin diminished the degree of fatty 
infiltration found in livers of trout lacking only 
dietary biotin. Whereas a total necrosis of kidney 
tubules occurred in only the pantothenate-deficient 
trout, intertubular deposits of glycogen were found 
in the kidneys of only the fish lacking biotin. 

Lake Trout Respond Negatively to Graded 
Levels of Dietary Fiber. — A study undertaken to 
measure the effects of diluting a practical type of 
diet with up to 32% cellulose showed a linear 
suppression of growth and feed use as the level of 
dietary cellulose increased. The higher levels of 
cellulose diminished digestible and metabolizable 
dietary energy and body fat. These results show not 
only that the dietary fiber is poorly used by trout, 
but also that it adversely affects fish growth and use 
of other nutrients. 

Nutritionally Induced Cataracts in Lake Trout. 
— Feeding diets containing a commercial soy 
protein isolate as the only protein induces a high 
incidence of cataracts. Therefore, the effect of 
supplementing this diet with amino acids (methionine 
and lysine), L-ascorbic acid, or minerals (calcium 
and phosphorus, or chrominum) on the develop- 
ment of cataracts was studied. The feeding of 
supplemental methionine and lysine prevented 
cataracts, but the use of supplemental minerals or 
ascorbic acid did not. 


Inland Fisheries and Reservoir 


Bacterial Gill Disease. — This is an infectious 
disease very similar to pneumonia of warm- 
blooded animals. It is a major cause of mortality 
among young cultured salmon and trout. Past 
investigations, as well as field observations, have 
shown that one type of waterborne bacterium is 
usually present and therefore may play an 
important role in causing the condition. However, 
all attempts to transmit gill disease with cultures of 
this bacterium have been unsuccessful. During the 
year, gill disease was induced in Atlantic salmon by 
crowding them and reducing their supply of water. 
The disease was then transmitted to young 
rainbow, brook, and cutthroat trout simply by 
supplying the trout with effluent water from the 
affected salmon. 

One means of preventing infectious diseases 

among cultured fishes is to eliminate contact 
between the pathogen and host. Many hatcheries 
must use stream water harboring carrier fish. 
Ultraviolet irradiation is used at several hatcheries 
to disinfect incoming water, but dosages required to 
kill fish pathogens are not yet known. Five 
important bacterial fish pathogens were tested for 
their susceptibility to several different levels of 
ultraviolet (UV) irradiation. Levels of 13,300- 
29,000 units (microwatt seconds per square 
centimeter) killed 99.96-100% of all organisms in 
clear water or in water containing particulate 
matter. Dosages as low as 4,450 units also effected a 
99.83-100% kill. 

The practicality of using UV in preventing actual 
infection was demonstrated by irradiating water 
that had passed over trout with furunculosis. 
Susceptible test fish failed to develop the infection, 
whereas 100% of the fish exposed to the 

Construction of the new National Fish Health Laboratory at Leetown, West Virginia, is proceeding on schedule. In the 
immediate foreground walls of the concrete tank pad have been laid. A completely glass-enclosed warmwater fish pond 
is shown on the right. A masonry garage (background) will abut the main laboratory, which was started in late 1976. 
Photo by H. M. Stuckey. 







Participants of the biennial comprehensive course on fish diseases are shown in the training laboratory. Six resident and 
six visiting scientists lecture and provide practical laboratory experience during a 5-month period. Photo by H. M. 

nonirradiated water died. Filtration of water before 
irradiation improved the efficiency of UV by 
removing particles that shield bacteria from the 
lethal UV. These results indicate that low UV 
dosages (13,300 units) kill bacterial pathogens 
naturally present in hatchery water supplies. 

Egg Transmission of Fish Diseases. — Some fish 
diseases are transmitted from parent to offspring in 
the eggs. This route of transmission was tested with 
viral infectious pancreatic necrosis (IPN) and 
bacterial furunculosis. The IPN studies were 
carried out jointly by the Eastern and Western Fish 
Disease Laboratories. Eggs and sperm obtained 
from brook trout with IPN were divided between 
the two laboratories. The resulting fertile eggs were 

further divided into four groups at each facility, two 
being disinfected with an organic-iodine complex 
and two remaining untreated. At both laboratories 
trout began to die soon after hatching, and IPN was 
eventually diagnosed in 7 of the 8 groups. The 
results show that IPN was transmitted with eggs 
and sperm and that disinfection with the iodine 
complex did not prevent the disease. Similar studies 
with furunculosis showed that the causative agent 
could not be detected either in eggs or sperm from 
carrier fish nor in their offspring. The inference is 
that, in contrast to IPN, furunculosis is not 
transmitted by eggs. The work will be repeated. 

Disease Diagnoses. — Fish health specialists 
make conclusive and sensitive diagnoses of diseases 


Fish Tealth News >^ 

A Service io ihc Field of Fish Health Research 



FISH HEALTH NEWS is a quarterly communication that is distributed as a service to diagnosticians and researchers by 
the Eastern Fish Disease Laboratory. Now in its 5th year of printing, circulation is expected to triple as individual requests 
can be honored. Photo by H. M. Stuckey. 

that occur in hatcheries or in natural populations. 
Serodiagnoses with specific antisera are the most 
rapid and accurate methods known, but they 
require standardized biological reagents, specific 
antisera, and antigens. In human and veterinary 
medicine, standardized antigens and specific 
antisera are produced by, and are available from, 
centralized Federal laboratories, and the more 
common reagents are even available commercially. 
The Eastern Fish Disease Laboratory provides the 
counterpart service for fish health diagnosticians. 
Antisera are produced by immunizing rabbits with 
specific fish pathogens, after which the rabbit blood 
serum is processed, tested, and freeze-dried for 
distribution to qualified diagnosticians and 
researchers. Shipments are accompanied with 
recommended procedures for reconstituting and 
using the products. Forms are also supplied to be 
filled in with the users' results. During the report 
year, over 300 requests for these materials were 
received and the reagents shipped. 

At present, stocked items include 35 different 
antisera and antigens. 

Present research is concentrated on continued 
improvement of the antisera and antigens, 
particularly on finding more effective methods of 
antigen preparation and rabbit immunization. In 
addition, larger batches of reference antigens are 
being processed to better standardize serodiagnostic 

Whirling Disease in Salmonids. — This disease is 
caused by Myxosoma cerebralis, a myxosporidan 
parasite accidentally brought into North America 
some 20 years ago. Severe infections of M. 
cerebralis result in death, and mild infections 
cripple or otherwise impair the host fish. 
Consequently, the parasite is a significant factor 
both in the propagation of trout and in their later 
survival in the wild. Methods have recently been 
developed for freeing the parasite from host 
cartilage and for concentrating it. For such 
diagnostic work, stained spores are used as markers 
to measure the efficiency of release and con- 
centration. A comparison of 1 1 dyes showed that 
silver nitrate provided the most lasting spore stain; 
the distinctive coloration persisted through 


processing and later storage for 1 Vi years. 

Serological methods, particularly the fluorescent 
antibody technique (FAT), provide positive 
identification of M. cerebralis and the most 
sensitive and earliest detection. Using FAT, we 
found evidence of infection 17 days after 
experimental exposure. The FAT is now carried 
out on a routine basis. The procedure has, however, 
revealed heretofore unknown biological relation- 
ships between M. cerebralis and other myxo- 
sporidans. In addition, FAT is being used to learn 
the life cycle of the parasite. 

Eel Virus. — The description of the eel virus, 
EV-1, has been completed and a manuscript has 
been written. Electron microscopy has established 
the size and shape to be similar to human influenza 
virus, a fact consistent with the findings of 
virological tests used in describing viruses. 

Among mammals, females transfer protective 
immunity to newborn offspring by colostrum, a 
special product in milk that is produced following 
birth. Such passive protection was demonstrated in 
rainbow trout fry that had been injected with adult 
brook trout antibody. The young rainbow trout 
were protected against levels of IPN virus that 
killed nearly 60% of the unprotected fry. The results 
have application in fish husbandry as a possible 
means of preventing loss. Further studies are under 

Long-term survival studies on clams are conducted in 
floating compartments to detect delayed mortality after 
exposure to antimycin, a fish toxicant. Photo by J. H. 
Chandler, Jr. 

However, long-term exposures at concentrations of 
5 to 20jug/l produced delayed mortality. 

In studies with the Asiatic clam, Corbicula sp., 
we explored the effects of time and concentration 
on mortality. All clams treated and left in antimycin 
solutions in test chambers for 30 days before 


Registration of Fish Toxicants. — The Fish Control 
Laboratories continued studies on techniques to 
control fishes. Antimycin is an effective fish 
toxicant that has been widely used to reclaim waters 
for sport fishing. Although a registration currently 
exists for this use, the data in hand are not adequate 
to support the reregistration required by EPA. 

Environmental effects of chemical applications 
are a continuing concern to ecologists and are a 
vital part of the data requirements for registration 
of any compounds. Unexplained mortalities of 
clams are sometimes observed several weeks or 
months after waters have been treated with 
antimycin. The effects of short- and long-term 
exposures of clams to the toxicant were measured 
in tests conducted at the Southeastern Fish Control 

There were no significant increases in the 
mortality of selected species of clams of 2yug/l for 
12 hours or 50/jg/l for 24 hours in test chambers or 
to 2 yug/1 indefinitely under pond conditions. 

The Asiatic clam, Corbicula leana, is an unwelcome exotic 
that is becoming established in many U.S. waters. 
Measurements of the shell are used to determine growth 
rates and to identify year classes. Photo by J. H. Chandler, 


transfer to untreated ponds died. On the other 
hand, clams exposed for 24 hours and then 
transferred to untreated ponds survived. Animals 
exposed to continuous low levels (3.6 fJ.g/\) of 
antimycin for 30 days died shortly after their 
removal to untreated ponds, but clams treated at 50 
>ug/l for 24 hours had much lower mortality when 
handled in a similar way. 

Use patterns in the treatment of waters for fish 
removal indicate that clams are unlikely to receive 
more than a 24-hour exposure to antimycin. 
Although changes in habitat that may result from 
the removal of fish could adversely affect clams, it 
appears that antimycin is not a direct cause of 
mortalities observed in treated rivers. 

Radio-labeled antimycin was used to study the 
breakdown of this compound. Exposure of 
solutions at pH 5 to longwave ultraviolet light for 
48 hours resulted in no significant degradation. 
Methanolic solutions were exposed to UV light for 
up to 24 hours and studied by exposure to X-ray 
film. Degradation was slow — only 64% after 24- 
hour exposure to UV light. Five as yet unidentified 
degradation products were observed. 

The hydrolysis of 14 C-antimycin at pH 9.2 was 
also studied. All samples degraded rapidly. Less 
than 50% of the parent compound remained after 4 
hours and only 12% or less after 5 days. Five 
degradation products were noted, one of which was 
presumed to be blastmycic acid. 

Although laboratory materials can be analyzed 
with fair resolution, problems were encountered 
when tissues from exposed fish were checked for 
residue levels. Residue methodology and data 
represent major voids in the available information 
base on antimycin. Without such data, re- 
registration is unlikely. 

Alternate fish toxicants are being studied as 
adjuncts to, or potential replacements for, the 
currently used materials. One promising candidate, 
coded GD-174, has shown a marked toxicity to 
carp but not to other warmwater fishes. In 
laboratory tests conducted in small pools, 0.5 ul/1 
killed all carp without loss of bluegills, largemouth 
bass, or channel catfish. All rainbow trout stocked 
in the pools were killed. Studies are under way to 
delineate the effects of algal blooms, plant growths, 
and turbidity and to determine the toxicity of GD- 
174 to other species of fish. If the selectivity 
observed in laboratory tests extends to field 
situations, GD-174 promises to be an effective new 
tool for the control of carp in fishery management. 

Currently available formulations of GD-174 lack 
uniformity of activity and have only a short shelf 

life. Both characteristics are under study and 
preliminary results suggest that neither will be a 
major problem. 

Thanite, an experimental fish-collecting aid, 
causes fish to float on the surface in a comatose 
condition. Fish transferred to clean, aerated water 
quickly recover. It has been postulated that Thanite 
could be used to selectively collect predator species 
or to collect desired brood fish. 

Field studies demonstrated that yellow perch, 
redear, bluegills, walleyes, crappies, largemouth 
bass, and redhorse can be collected with survival 
rates up to 99%. Golden shiners, white suckers, 
bullheads, and northern pike are less easily 
collected and may have lower survival rates. No 
northern pike recovered after transfer to clean, 
aerated water. 

Degradation or loss of activity occurred in 8 days 
at temperatures of 18° to 23° C and pH's of 4.9 to 

A pond treated in October 1974 was studied over 
the ensuing 2 years and collections were made to 
assess possible environmental effects. Planktonic 
crustaceans were reduced by 80 to 90% 7 days after 
treatment. Six months after treatment, micro- 
crustacean populations began to recover and 
continued to increase for 1 year. However, Daphnia 
numbers did not return to pretreatment levels and 
Diaptomus disappeared and did not return. 
Benthic populations were not significantly altered 
by the chemical application. 

A method for the determination of Thanite 
residues and metabolites in water, mud, algae, and 
fish tissue was developed. Residues were found for 
3 weeks but not thereafter. A major metabolite 
found in fish tissue has been identified as a thio- 
ether of Thanite. Isoborneol also occurs as a residue 
in fish tissue. 

Registration of Therapeutants for Fish. — 
Formalin is widely used for the treatment of 
external parasites of fish. Studies to determine 
ecological effects revealed that fish in treated ponds 
survived well, spawned, and produced a normal 
crop of young-of-the-year fish. Oxygen levels were 
temporarily depressed but returned to normal in 5 
days under pond conditions. Benthic organisms in 
treated ponds were not affected. 

Applications made in plastic pools having a 
dense algal bloom indicated that the formalin may 
kill the algae and that the combined effects of 
chemical depression of the oxygen level, coupled 
with the oxygen reduction caused by decaying 
algae, may result in an oxygen depletion and fish 


Malachite green, a parasiticide and fungicide, is 
suspected of having physiological effects on fish 
and fish eggs. Rainbow trout fingerlings were con- 
tinuously exposed to a sublethal concentration in 
flow-through systems. After 28 days no marked 
alterations could be detected in the blood chemistry 
of treated fish. 

Laboratory tests confirmed empirical evidence 
that the toxicity is related to concentration, length 
of exposure, and temperature but that it is not 
affected by pH or water hardness. 

Hatching was delayed in eggs of rainbow trout 
exposed to malachite green at 1 mg/1 for 1 hour 
daily, 3 mg/1 for 1 hour every other day, or 5 mg/1 
for 1 hour weekly. The incidence of abnormalities 
was 2.5 to 7 times that of untreated eggs, and 
growth rate of all fry from treated eggs was reduced. 

Bacterial gill disease is a continuing problem in 
the production of trout and salmon and is 
particularly troublesome in hatcheries rearing 
Atlantic salmon. Furanace, a nitrofuran drug, is a 
therapeutant that effectively controls bacterial gill 
disease. However, the drug is not registered for use 
on food fish or on hatchery fish that eventually 
might become food fish. 

Studies at the Fish Control Laboratories 
demonstrated that the activity of Furanace is not 
affected by pH or water hardness. Rainbow trout 
exposed to recommended use pattern rates for three 
consecutive days exhibited no mortality or 
abnormal behavior. The toxicity to trout increases, 
however, with rising water temperatures and 
increased exposure times. Freshwater prawns, 
snails, and Asiatic clams were not affected by 
concentrations of Furanace up to 20 mg/1 for 1 
hour. Other studies indicated that Furanace 
solutions retain their activity for over 6 weeks. 
Consequently, effluents from hatcheries where 
Furanace is used are likely to contain significant 
concentrations of the compound. 

If Furanace could be removed from hatchery 
effluents, concern over possible environmental 
contamination would be greatly reduced. Data 
developed at the Fish Control Laboratories show 
that Furanace can be effectively removed by 
activated carbon filtration. In cooperative studies 
with the Green Lake National Fish Hatchery, 
Ellsworth, Maine, a prototype filter system 
effectively removed the drug from treated water 
under hatchery production conditions without 
stressing the treated fish, and with little incon- 
venience to hatchery operations. Effective removal 
techniques will greatly reduce concerns over 
environmental contamination resulting from the 

use of Furanace and should expedite amended 
registration of fishery uses in the control of 
bacterial fish diseases. 

Unexplained variations are observed in the 
responses of fish to fishery chemicals. It has been 
hypothesized that the presence of other environ- 
mental contaminants may greatly affect the toxicity 
of treatments. To test this hypothesis, we divided a 
lot of rainbow trout into three groups, and exposed 
one group to 0. 1 ;ug/l of the PCB, Aroclor 1254, and 
another to 0.01 jug/1; the third group served as 
untreated controls. After 30 days of exposure, 
whole body residues were 0.28jug/g and 2.31 /ig/g 
for the respective exposed groups and their 
sensitivity to several fishery chemicals was then 
determined in standard toxicity tests. Included in 
the tests were rotenone, antimycin, GD-174, TFM, 
formalin, malachite green, Furanace, MS-222, 
copper sulfate, and 2,4-D:DMA. 

Most of the chemicals were unaffected by the 
presence of the PCB residues, but both groups of 
exposed fish were more resistant than the controls 
to antimycin and malachite green, and were more 
sensitive than the controls to rotenone and 2,4-D. 

Registration of Anesthetics for Fish. — 
Anesthetics used to sedate or narcotize fish must 
also be registered by the Food and Drug 
Administration. Materials submitted with appli- 
cations for registration lacked data on residue 
persistence. Studies during the year indicated that 
no residues of the two most commonly used 
anesthetics, quinaldine sulfate and MS-222, were 
present in fish tissues 24 hours after removal of the 
fish from the anesthetizing solutions. When the two 
compounds were used together at recommended 
levels, no residues were found after 24 hours. The 
results provide assurance that fish can be effectively 
anesthetized without concern about undesirable or 
potentially hazardous residues in treated fish. This 
finding is significant because many brood fish and 
fingerlings are exposed to anesthetics in the normal 
hatchery production of fish for public waters. 

Counteraction and Removal of Chemicals Used 
in Fisheries. — A prototype filter system developed 
at the Fish Control Laboratories continues to find 
application beyond its original drug removal 
purpose. Use of other filter media in the system 
greatly expands its potential use. One such use 
would be for the removal of ammonia from 
hatchery effluents. 

Three resins (XAD-7, Biosorb, and pH filter 
resin) and clinoptilolite, a form of zeolite, were 
evaluated for their effectiveness in removing 
ammonia from water. A 2-liter stock solution of 


A prototype filter system developed at the Fish Control 
Laboratory effectively removes most chemicals used to 
control fish diseases without stressing the animals. Photo 
by L. L. Marking. 

10mg/l NH 3 as N was filtered through a 15-cmbed 
of each. The effluent was sampled at selected volume 
intervals and ammonia concentrations were 
determined by specific ion electrode analysis. 
Clinoptilolite was the most effective adsorber, 
removing all detectable ammonia from the 2-liter 
stock solution. Biosorb and XAD-7 were also 
effective adsorbers, but detectable levels of 
ammonia were present in the effluent after 600 ml 
had passed through the filters. The pH filter resin, 
the least effective adsorber, removed almost no 

In separate studies, the effects of water pH on 
adsorptive capacity of clinoptilolite for ammonia 
were evaluated. Clinoptilolite was about 60% less 
effective for removing ammonia from water of pH 
6.5 than from water of pH 9.5. Although 
clinoptilolite has a strong affinity for ammonia, it 
does not remove nitrates or nitrites, both of which 
are potentially toxic to fish. 

The effects of temperature, water hardness, and 
pH on the toxicity of nitrate to rainbow trout, 
channel catfish, and bluegills were determined. 
Toxicity of nitrate nitrogen to these species 
increased with exposure time, and generally was 
not affected by the temperatures, hardnesses, or 

pH's, but it was significantly more toxic to rainbow 
trout in soft, acid water of pH 6.5 than in alkaline 
water of pH 9.5. 

The toxicity of nitrite nitrogen to rainbow trout, 
channel catfish, and bluegills at selected temperatures, 
hardnesses, and pH's was determined. In rainbow 
trout, the toxicity of nitrite was not affected by the 
different water temperatures, but was significantly 
increased in soft waters and in water of low pH. In 
channel catfish, toxicity was not significantly 
affected by water temperature or pH, but it was 
significantly greater in soft water than in hard 
water. In bluegills, toxicity was significantly greater 
in warm than in cold water and in soft, acid water 
than in neutral or alkaline water. Under the same 
test conditions, nitrite was 145 times more toxic to 
rainbow trout and 233 times more toxic to channel 
catfish than it was to bluegills. 


Biological Filters to Remove Fish Growth 
Depressants. — Metabolic excretions and other 
growth depressants limit the reuse of water in fish 
production. However, the reuse of part or all of the 
water in which fish were previously cultured 
conserves this limited resource for higher priority 
programs; also, pollution of the environment is 
reduced when organic contaminants are removed 
from the discharge water. 

Passive systems that take advantage of natural 
heat and oxygen are desired, because they require 
little additional energy. Of the various filter types 
tested, water hyacinth, which has caused so many 
problems in southern warmwater lakes and rivers, 
has been found to efficiently remove organic waste 
metabolites, heavy metals, and other waterborne 

A filter system that shows considerable promise 
in water reuse consists of tube settlers. This system 
has an advantage over aquatic plants in that no 
sunlight is required, and it is therefore adaptable to 
indoor facilities. Our analytical data show that the 
tube settlers are 3 times more efficient in removing 
suspended solids and over 20 times more efficient in 
removing settleable solids than are water hyacinths. 
Thus, this filter sysem appears to be satisfactory for 
oxidizing soluble metabolites in culture systems. 
Draining Methods for Decreasing the Amount of 
Settleable Solids in Effluents from Fish Ponds. — 
Controlled draining should limit the amounts of 


settleable solids in pond effluents. However, no 
documented studies on the effect of controlling the 
flow from bottom-drain fish ponds are available. 

To obtain meaningful information on which 
EPA might base discharge criteria, we stocked test 
ponds with carp, a bottom "rooter" that tends to 
keep a pond turbid. The drain was opened at 
preselected intervals to obtain samples of effluent. 

As the drain opening (flow rate) was increased, 
the maximum instantaneous values for settleable 
solids usually increased, but at mean flow rates 
above 723 1/min these maximum values decreased. 
Controlled draining apparently decreased the 
settleable solids. However, the total settleable 
solids discharged in 10 minutes usually decreased as 
the flow rate increased. Flow rates of 88 1/min or 
more were of sufficient velocity to move solid 
particles of the density occurring in this pond. A 
lower flow rate probably would not carry particles 
from this pond; however, the use of an extremely 
low pond discharge rate as a method for reducing 
solids in effluent would not be practical in intensive 
fish culture because of the long time that would be 
required to drain large ponds. 

Management Methods for Removing Particulate 
Matter in Effluent from Fish Ponds. — The 
production of warmwater fish in earthen ponds no 
doubt affects the water quality and aquatic life in 
streams receiving the effluent; however, little is 
known about the quantities of solids generated in 
intensive fish culture. Such information on the type 
and amounts of solids produced by the various fish 
species in the different culture programs would 
permit the establishment of control methods. The 
manager could then comply with EPA effluent 
regulations and also meet his fish production 

Fish density affects the amount of solids 
produced in the aquatic system, as one might 
suspect. However, the amount of suspended and 
settleable solids measured in ponds stocked and 
managed according to current recommendations 
for commercial fish production were not significantly 
different from those measured in fish-free control 
ponds. Only when stocking levels were doubled to 
4,000 fish per acre were we able to detect 
deterioration in water quality. 

We anticipated that another species, such as the 
grass carp, would permit recycling of nutrients, 
including phosphorus and nitrogen, and thus 
reduce the production of phytoplankton. The 
phytoplankton, after dying and decaying, contributes 
largely to the collection of materials we describe as 
settleable solids. This apparently occurred, as the 

average production of solids was 1.7 times greater 
in fish-free control ponds than in ponds with grass 
carp. Moreover, average production of solids was 
slightly (but not significantly) less in ponds with 
grass carp than in those with channel catfish. 

Results of studies not yet completed suggest that 
the stocking of fathead minnows with channel 
catfish does not decrease the production of 
settleable and suspended solids. 

It does appear that catfish production levels 
affect the amount of pond solids produced, 
although not as much as one might guess. However, 
the lower amounts of solids measured in ponds with 
grass carp strongly suggest that the use of this 
species in combination with channel catfish will 
reduce the solids in the effluent of ponds. 

Identity of the Ubiquitous Anchor Parasite, 
Lernaea. — Since 1950 the dangerous Lernaea that 
will attack any species of freshwater fish has been 
known as Lernaea cyprinacea. Researchers in the 
USSR have also been concerned with this parasite, 
and study of exchanged specimens revealed that the 
common American parasite is actually L. elegans. 
The other one, L. cyprinacea, attacks only goldfish. 
It is important to fish culturists to know that L. 
cyprinacea will not spread to other fish species but 
that L. elegans will. The two can be easily 
distinguished by the shape of the dorsal arms of the 
"anchor" which are T-shaped in L. cyprinacea and 
Y-shaped in L. elegans. 

Asian Tapeworm Found in North American 
Fishes. — The Asian tapeworm, Bothriocephalus 
gowkongensis, has traveled with the grass carp 
from its original habitat in eastern Asia (Amur 
River) across Asia and southern Europe, and to the 
United States and elsewhere. In Europe it is now a 
serious parasite which often kills young carp. In the 
United States, Fish Farming Experimental Station 
employees found the tapeworm in bait minnows 
(golden shiners and fathead minnows), and workers 
at Auburn University found it in grass carp. The 
parasite is not identical to any of the known North 
American species and therefore is truly the Asian 
tapeworm. A publication describing this pathogen 
and methods of controlling it is being prepared. 

Ovarian Parasite Found in a New Host. — The 
ovarian parasite, Pleistophora ovariae, of golden 
shiners has been known for 12 years. The parasite 
destroys developing eggs in the fish. It was recently 
found to occur also in the fathead minnow. The 
incidence appears to be low, but fish culturists 
wishing to avoid P. ovariae should keep this record 
in mind, to avoid transferring the parasite to a new 


Marking Techniques for Channel Catfish. — 

Identification of individual fish or groups offish is 
almost essential in selective breeding, physiology, 
and other research programs, and most fish 
management studies. Channel catfish are particularly 
difficult to mark since they do not have scales. The 
external application of silver nitrate, which 
cauterizes the skin, was compared with seven 
commonly used marking or tagging techniques: fin 
clipping; hot branding; cold branding; dye 
injections; and the application of Floy tags, ring 
tags, and dangler tags. After 4 months, mark 
retention was poor in all but silver nitrate and hot 
branding groups. Hot branding required a car 
battery and was the less versatile of the two 
methods because the blade of the branding iron was 
fixed. Fins had partly or completely regenerated on 
80% of the fin-clipped fish. Cold brands faded 
rapidly and only 28% could be positively identified. 
Only 4% of the dye-injected fish were identifiable. 
All three tags caused lesions on the fish; many tags 
were lost, and the tags that remained were covered 
with algae and required scraping before the 
numbers could be read. 

Fish branded with silver nitrate had easily 
distinguishable marks that have been retained for 
more than a year. Time and labor required to apply 
the silver nitrate mark are not prohibitive. Thus it 
appears that this technique is suitable for marking 
and identifying catfish. 

Mollusks for Removing Growth Suppressant 
Factors in Fish Cultural Systems. — When 
mollusks were stocked in combination with channel 
catfish in static culture systems, the growth rate of 
the catfish increased over that of catfish stocked 
alone. This suggests that the mollusks remove 
growth suppressants, and thus are potentially 
valuable for incorporation into a practical closed 
fish-production system. 


Research at the Fish Genetics Laboratory is 
expected to yield two principal results: (1) a 
definition of the strain of rainbow trout that is best 
suited to meet a specific management objective, and 
(2) definitions of how these fish can be produced in 
our existing hatchery system. These objectives are 
approached through a variety of genetic studies as 
outlined below. 

Strain Characterization. — Ten distinctive 
strains, 12 inbred lines, and 9 strain crosses are 
being maintained for genetic characterization. 

Heritability estimates are obtained for a variety of 
morphological attributes (e.g., number of vertebrae) 
and production traits (e.g., growth), and the degree 
of genetic correlation among combinations of these 
traits is defined. Strains are also characterized by 
measuring the frequency of variant enzymes for 
each of 15 tissue enzyme systems examined by 
electrophoresis, and competition efficiency for use 
of a natural food supply is measured in terms of 
growth and survival. Comparisons of performance 
at different hatcheries, and return of fish to the 
fisherman after release, are obtained. Finally, each 
strain is ranked according to its overall efficiency, 
and causes for differences in efficiency are sought 
among the genetic differences which characterize 
the strain. 

Although the study is now only about 20% 
completed, numerous strain differences have been 

Inbreeding Effects. — Inbreeding is the result of 
using small numbers of parents to produce a brood 
stock. This practice is apparently relatively 
widespread, judging by our review of brood stock 
management practices. Inbreeding has been shown 
to increase costs and decrease overall efficiency. 
Continuing studies have demonstrated that inbred 
trout are more vulnerable than outbred fish to 
stressful situations, such as the presence of 
toxicants or elevated temperature. Because 
inbreeding is expressed as a generalized debility, we 
suspect that some nutrition and disease problems 
may in fact be largely inbreeding problems. 

Cooperative Studies. — Field tests of four 
rainbow trout strains supplied to the Bozeman Fish 
Cultural Development Center were completed. The 
New Zealand strain, which grew to the greatest size 
after release (and showed high survival), yielded the 
poorest growth and food conversion efficiency in 
the hatchery before release. This result shows that 
performance in the hatchery is not necessarily a 
good index of performance after planting. 

A reverse of this situation was observed in tests of 
five strains at the McNenny Diet Development 
Center. Plant proteins were substituted for fish 
meal as protein sources to the extent that herring 
meal constituted only 6% of the diet and soybean 
meal 40%. Strains which showed good growth 
and conversion efficiency on this diet also 
performed best on different diets containing 
herring meal as the main protein source. 

Blood chemistry studies on inbred and outbred 
trout performed in cooperation with the Western 
Fish Disease Laboratory indicated that blood 
glucose levels were higher in inbred groups than in 


outbred controls. Because elevated blood glucose 
levels are indicators of stress, it appears that inbred 
trout are experiencing stress under mild conditions 
that are less stressful to outbred fish. 

Studies on Efficient Design of Experiments. — 
The validity of heritability estimates is usually 
indicated by the magnitude of their standard errors. 
We have shown, however, that standard errors are 
in fact random variables that may assume a broad 
range of magnitude in repeated experiments of the 
same size and design. The range of magnitudes is 
greatest in small experiments. Poorly designed 
experiments can thus often yield results judged to 
be meaningful because of small standard errors. 
Size of experiments required is partly a function of 
the true heritability being estimated. Consequently 
we have defined, for different heritability levels, the 
size of experiments required to minimize the 
possibility of being misled by erroneously small 
standard errors. 


Inventory of Reservoirs. — A nationwide inventory 
of reservoirs larger than 500 acres, compiled in 
cooperation with state fishery agencies, indicated 
that 1,493 existed in January 1976, totaling 
9,774,000 acres at average water levels. Seventeen 
states in the southern and northwestern United 
States contain three-fourths of the total area. 
Three-fourths of the total number are in 21 states in 
the south, west, and north-central regions. 
Reservoir angling is concentrated in southern and 
north-central states, and California. Since 1960, 
about 487 reservoirs have been impounded, 
encompassing 3,324,000 acres — an increase of 
52%. However, the pace of reservoir construction 
has slowed in recent years. 

Current reservoir field research of the Fish and 
Wildlife Service is centered in Arkansas, South 
Carolina, and South Dakota; emphasis is on 
problems associated with the effects of nuclear 
plants, pumped storage operations, and water 
withdrawal from various depths on fishery 
resources in the impoundments and their tailwaters. 
A major aim of the National Reservoir Research 
Program involves the collection and analysis of 
physicochemical and biological data on large 
reservoirs throughout the Nation. The goal is to 
examine large masses of data and identify 
important relationships between environmental 
conditions and reservoir operational regimens and 

the resulting biological production and sport fish 
abundance and harvestability. 

A recent concerted effort to obtain all existing 
information on reservoir sport fish harvest and 
angler use has resulted in a doubling of the data 
base available 5 years ago and set the stage for 
marked improvements in our ability to predict 
harvest and angler use in planned or existing 

Predator Fish Stocking Evaluation. — We 
completed the analysis of data obtained from a 2- 
year study of 26 reservoirs where predators 
(primarily striped bass and walleyes) were stocked. 
The field research was conducted under the 
auspices of the Reservoir Committee, Southern 
Division of the American Fisheries Society, and 
involved 1 1 State and 2 Federal fishery agencies. A 
method of estimating available prey-predator 
relations in reservoirs was developed, based on fish 
standing crop data derived from samples collected 
in rotenone-treated coves. After we determined the 
sizes of prey species that predators with various 
mouth sizes could swallow, we adjusted other 
species of predators to equal largemouth bass, and 
developed a computer program to calculate the 
biomass of prey available to "bass-equivalent" 
predators, 1 to 28 inches long, by 1-inch length 
groups. Results indicated that 50% of the 
populations sampled in August were deficient in 
available prey. Stocking of additional predators in 
these waters would be deemed inadvisable. 

Average available prey/ predator ratios were 
lowest in the standardized (bass-equivalent) 8- to 
1 2-inch predator length classes. Greatest potential 
competition for food apparently occurs in this 
length range, which consists largely of 1- to 3-year- 
old predators. 

The development of the computer simulation of 
available prey-predator relations provides fishery 
managers with an instantaneous estimate of the 
adequacy of the prey base and the advisability of 
stocking more predators or introducing more prey 

Prediction of Fish Production. — To exemplify 
the uses which fishery management agencies may 
make of reservoir fish crop and harvest estimators 
derived from correlation and regression analysis, 
we undertook prediction of fish production in 
Oklahoma reservoirs on the basis of standing crop 
data from 20 of that State's 50 impoundments. 
Testing of 10 environmental variables revealed a 
strong positive influence of low storage ratio (i.e., 
high water exchange rate) on total fish standing 
crop. The crop of such bottom-feeding fishes as 


carp, buffalofishes, freshwater drum, adult shad, 
and carpsuckers made up 70 to 85% of the total 
crop, and accounted for the increase in total crop as 
water exchange rate increased. This points to a need 
to intensify study of the relations between fish 
production and seasonal timing, volume, and 
quality of streamflows through reservoirs. The 
manipulation of water exchange rates represents a 
valuable fish management technique. 

In the hypothetical annual production of major 
fishes in Oklahoma reservoirs, estimated from 
standing crop data, the dominance of bottom- 
feeding fishes was apparent. Organic detritus from 
vast watersheds and upstream reservoirs, plus in- 
lake production of bottom organisms, supplies the 
food required for high production of bottom- 
feeding fishes in reservoirs with high water 
exchange rates. If 40% of the total food requirement 
is provided by washed-in organic detritus, more 
management attention should be given to the 
watershed, to vegetation in the water level 
fluctuation zone, to accumulative effects in a chain 
of reservoirs, and to detrital materials which would 
enhance production of sport fish rather than rough 

Modeling Reservoir Fisheries. — Under a 
cooperative agreement with the Ecosystem 
Research and Simulation Division of the Waterways 
Experiment Station, U.S. Army Corps of Engineers, 
Vicksburg, Mississippi, we have developed a fishery 
submodel which is to be incorporated into a larger 
mathematical reservoir system model being 
designed by the Corps' Waterway Experiment 
Station. An extensive literature search was 
completed to develop: (1) food data on 78 reservoir 
fish species; (2) maximum specific growth rates for 
46 species; (3) digestive efficiencies for various 
species; (4) annual, daily, and instantaneous 
natural mortality rates for various species; (5) 
regression formulas relating active and standard 
metabolism at various temperatures to fish weight; 
and (6) temperature tolerance and preference data 
for various species. 

In addition, by using recent findings and 
hypotheses derived from analyses of standing crop 
and harvest data by the National Reservoir 
Research Program, we estimated the following 
needed inputs to the model for reservoirs in seven 
major drainage areas: (1) distribution of fish 
biomass supported by five fish-food compartments 
(detritus, plankton, benthos, fish, and terrestrial); 
(2) distribution of fish-carrying capacity and 
annual production among the fish food compart- 
ments; (3) carrying capacity of principal fishes; (4) 

annual sport and commercial fish harvest 
supported by various food compartments; and (5) 
amount of food ingested that results in fish growth 
of one-half the maximum rate. 


Phytoplankton Production Varies Among Four 
South Dakota Reservoirs. — Preliminary obser- 
vations in the four lowermost Missouri River 
reservoirs indicated that some areas were consistently 
more productive than others. A better understanding 
of the spatial pattern of primary production and the 
factors responsible for change was the subject of a 
2-year study. Several permanent study areas were 
established from lower Lake Oahe to lower Lewis 
and Clarke Lake, and measurements of phytoplankton 
standing crop, photosynthesis, and related physical 
and chemical characteristics were obtained at each 

Biological conditions along this 300-mile stretch 
of the Missouri River reservoir system varied 
significantly. Areas of high production and high 
standing crops of phytoplankton were similar in 
many respects to the more eutrophic areas of the 
Great Lakes (e.g., Green Bay in Lake Michigan), 
whereas areas of low production and low 
phytoplankton standing crops were similar to the 
oligotrophic areas in the Great Lakes (e.g., offshore 
Lake Superior). 

The spatial pattern of phytoplankton production 
in the four reservoirs can be explained as follows: 
(1) movement of water in the system is uni- 
directional (i.e., downstream); (2) production in the 
transient water mass is characteristically low and is 
limited by available phosphorus; (3) tributary 
streams entering the reservoirs are important 
sources of phosphorus enrichment, and a plume of 
increased phytoplankton production extends 
downstream from the mouth of each major 
tributary; and (4) in some areas, vertical mixing of 
surface water below the limit of light penetration is 
an added factor regulating phytoplankton photo- 

Effects of Power Plant Operations on Reservoir 
Biology. — The effects of variable water discharges 
from hydroelectric power plants (peaking) on fish 
and plankton standing crops in downstream 
reservoirs are not well known. A study was 
conducted in 1974 and 1975 to determine the effects 
of peaking on the stocks of zooplankton and larval 
fish in Lake Sharpe, South Dakota. This reservoir 


is impounded by Big Bend Dam; its headwaters 
extend to Oahe Dam. Plankton net sampling was 
conducted in the tailwaters of Oahe Dam and in the 
headwaters and tailwaters of Big Bend Dam. 

The higher the water releases from Oahe (inflow), 
the lower was the number of zooplankters per liter 
discharged into Lake Sharpe. No similar relation 
was found for releases from Big Bend Dam 
(outflow). The observed difference was probably 
due to differences in the design of the powerhouse 
water-intake systems at the two dams. 

Zooplankton standing crops in Lake Sharpe 
were influenced more by the total seasonal inflow 
than by the daily inflow cycle. Sustained high water 
releases from Lake Oahe in 1975, compared with 
those in 1974, were associated with changes in the 
composition of the zooplankton discharge. The 
percentage of calanoid copepods in the inflow from 
Oahe increased in 1975, the percentage of 
cladocerans decreased, and the percentage of 
cyclopoid copepods remained the same. There was 
a similar increase of calanoid copepods in Big Bend 
outflows; however, the percentage of cladocerans 
increased and the percentage of cyclopoid 
copepods decreased. The mechanisms responsible 
for the observed shifts in composition are not 
known. The number and weight of zooplankton per 
liter was greater in water releases from both dams in 
1975 than in 1974 — probably a result of the higher 
reservoir water levels and discharges during 1975. 
The magnitude of plankton exchange is indicated 
by the finding that Lake Sharpe gained an 
estimated 5,200 metric tons of zooplankton from 
Lake Oahe during a single week in May 1974. 

We were unable to quantitatively measure losses 
of fish eggs and larvae from either Lake Oahe or 
Lake Sharpe because of sampling problems. Eggs 
and larvae of freshwater drum were most abundant 
in collections in both 1974 and 1975. Those of carp 
were second in abundance in 1974, a low-water 
year; and yellow perch and buffalo were second and 
third in abundance in 1975, a high-water year. 

Fish Spawning in Lake Oahe. — Knowledge of 
the spawning biology of fishes is basic to 
understanding the ecology of species and is also 
useful in planning the annual water regimen for 
Lake Oahe, a large Missouri River storage reservoir 
in South Dakota. In a recently completed study the 
timing and sequence of spawning of 17 common 
fishes were determined from an examination of 
ovaries. Changes in the mean ovary indices (ratios 
of ovary weight to fish length) indicated that 
development of eggs to seasonal spawning lasted 
l x /i to 10 months, depending on species, and 

spawning of individual species lasted 2 to 16 weeks. 
Over an 8-year period (1964-71), annual variations 
in the date of peak spawning were usually less than 
a week. Although the spawning period of some 
species overlapped, peak spawning dates seldom 
coincided, and there was an established sequence of 
spawning among species. 

The frequent occurrence of ovaries with 
degenerating eggs during the last several years of 
the study appeared to indicate that spawning 
conditions in this fluctuating reservoir were 
unfavorable for shovelnose sturgeon, northern pike, 
and carp. 

Distribution and Abundance of Young Fish in 
Lake Sharpe. — Studies of the young-of-the-year 
fish stocks in Lake Sharpe, South Dakota, were 
conducted from 1967 to 1975 to determine their 
spatial distribution and to assess annual reproductive 
success by species. This work is part of a program to 
determine the influence of water management by 
the U.S. Army Corps of Engineers on reservoir fish 
populations. Samples were collected semimonthly 
from late June to early September with a 
standardized haul seine and a 27-foot otter trawl. 

Thirty-nine fish species were collected, and the 
catches of both gears indicated similar trends in the 
distribution and relative abundance of most 
species. Catches were usually highest in the middle 
third of the reservoir, and a single, relatively small 
backwater area, known as Hippie Lake, accounted 
for about 40% of the total catch. Midsummer 
catches were highest for most species in all areas 
except the upper reservoir. Peak catches in the 
upper area were in late summer, probably due to 
upstream migration of the young fish. 

Gizzard shad and yellow perch accounted for 
over 80% of the seine catch, whereas gizzard shad, 
yellow perch, black crappies, and white crappies 
accounted for about 90% of the trawl catch. 
Highest abundance of the principal species was in 
1968. From 1972 to 1975, seine and trawl catches 
remained nearly stable, except for a 48% decline in 
the trawl catch from 1974 to 1975. Abundance of 
walleyes, the primary game fish in Lake Sharpe, 
remained relatively stable during 1971-75. Four 
species — freshwater drum, white bass, bigmouth 
buffalo, and smallmouth buffalo — increased in 
abundance during this same period. Most other 
species decreased. 

There has been a tendency toward stabilization 
of the young-of-the-year fish stocks since 1971. 
Except for walleyes, adult predator species have 
been greatly reduced from earlier years, and most 
forage species have declined. Thus, the population 


structure in Lake Sharpe is likely to continue to 
consist of a dominant predator (walleye) supported 
by a variety of young-of-the-year of other species. 

Biology of Yellow Perch in Lake Sharpe. — The 
yellow perch is one of the primary foods of the 
walleye in Lake Sharpe. Because of its importance 
as prey, the yellow perch population was studied 
from 1964 to 1975 to (1) determine the characteristics 
of the population, including distribution, abundance, 
age, growth, and mortality, and (2) determine 
factors affecting these characteristics. Young fish 
were sampled with seines and otter trawls, and 
older fish with gill nets. 

Yellow perch spawn in tributary embayments, 
and the young spend their first summer of life in 
these protected areas. They move into deeper 
waters of the reservoir beginning about mid- 
September, and some young fish tend to migrate 
upstream in the reservoir. Growth of the young is 
fastest in the lower portions of the reservoir and 
slowest in the upper portions. Growth rates 
increased in recent years and were inversely related 
to the abundance of emerald shiners. 

The most successful year class of yellow perch 
was produced in 1964, the first year after 
impoundment of Lake Sharpe. Although spawning 
was successful in every year, no later year class 
entered the adult stock in large numbers. Adults 
were most abundant in 1967, but their numbers 
declined markedly and remained low after the 1964 
year class died off. The fish are relatively short- 
lived; females rarely surpassed age IV or males age 
III. Growth rates of both males and females, which 
did not differ significantly, have increased in recent 
years. The sex ratio of adults apparently changed 
from about two females per male in the mid-1960's 
to about six females per male in the mid-1970's. 


Underwater Observations of Black Bass Repro- 
duction. — Studies of the sympatric spawning of 
black basses, their nesting requirements, and 
reproductive potential continued in Bull Shoals 
Lake during 1976. Underwater observations were 
conducted each week from April 13 through June 3, 
in five study areas representing bluff and cove 

Spawning by largemouth, smallmouth, and 
spotted bass began on or about April 3, about 2 
weeks earlier than the average date of first 

spawning observed since 1967. Although water 
temperatures were relatively high, they were still 
only marginal for spawning on April 6, when the 
temperature at 1 m depth was 13.6° C. Later lake 
warming was much slower than in 1975, when the 
rapid increase in water temperatures shortened the 
periods of egg incubation and larval development. 
The survival rates of eggs and larvae were not as 
high during the cooler, more prolonged spawning 
period in 1976. However, largemouth bass fry 
production was much greater than in 1975, 
primarily because nest densities were very high — 

8.8 per 100 m of shoreline at the bluff and 9.5 per 
100 m of shoreline in coves (about 4 times the 
highest density recorded during the previous 9 
years). This great increase in the largemouth bass 
spawning population was presumably due to the 
participation of the very strong 1973 year-class. 
Smallmouth and spotted bass nest densities in 
coves were near the 10-year average. However, 
along the steep shoreline, spotted bass nest densities 
were high (15/100 m) and smallmouth bass nest 
densities were low (0.3/ 100 m). 

The water level in Bull Shoals Lake at the 
beginning of bass spawning was about 1 m above 
conservation pool level and fluctuated less than 1 m 
during the entire spawning season, keeping the 
bases of shoreline willow trees flooded to a depth of 
1 to 2 m. Bull Shoals Lake was extremely clear 
during most of the spawning season; Secchi disc 
transparencies ranged from 8.2 to 13.3 m (mean, 
1 1.8 m) at the bluff, and from 3.6 to 13.5 m (mean, 

7.9 m) in coves. Despite the clear water, largemouth 
bass nested at relatively shallow depths in coves 
(mean depth, 1.5 m), apparently selecting areas 
where partly flooded willows afforded cover. Of the 
largemouth bass nests in coves, 90% were beside the 
bases of willows where the cleaned substrate 
consisted at least partly of exposed roots and 
rootlets. Spotted bass nests in coves were frequently 
found in habitat and on substrate similar to that 
used by largemouth bass, but also in a greater 
variety of habitats and at a greater mean depth 
(2.7 m). Smallmouth bass appeared to select gently 
sloping rock and gravel bottoms as nesting habitat, 
with a mean nest depth of 2.8 m. 

Incidental to the study of bass spawning were 
observations of crappie nesting which occurred 
simultaneously with that of bass in the Bull Shoals 
Lake study areas. Nests of black crappies and white 
crappies were found near the bluff, on similar 
substrate and at the same depth (mean, 9 m). In 
coves the nest depth and substrate of the two species 
differed: white crappie nests were in rocks and 


Male smallmouth bass guarding fry in nest, Bull Shoals 

Male spotted bass guarding nest of eggs in Bull Shoals 
Lake. Nest substrate of rocks and waterlogged branches is 
frequently used by this species. 

gravel at a mean depth of 6.8 m, whereas those of 
black crappies were usually at the bases of willows 
or in adventitious roots on the trunks of willows, at 
a mean depth of 1.3 m. 

Production Estimates of Young-of-the-year 
Shad. — Production of young-of-the-year shad in 
Beaver Reservoir, determined for a period June 9 to 
September 2, 1976 by mid-water trawling, was 
below average; estimates were 82 kg/ ha in the 
upper portion of the reservoir, 23 kg/ ha in the 
middle, and 6 kg/ha in the lower portion. 
Production of young-of-the-year shad was also 
estimated at 67 kg/ ha for a 52-ha cove in the middle 

Two sets of comparison tests were made between 
a larval fish trawl developed in 1971 and a new 
"Tucker" trawl. Results indicated the Tucker trawl 
to be 3 times more effective than the other trawl for 
capturing young shad in June and July. 

Sampling Fish Populations in Coves. — 
Systematic annual sampling of fish by treating 
coves with rotenone has been conducted annually 
on Beaver and Bull Shoals lakes since 1968. These 
long-term studies have permitted evaluation of 
relations between changes in fish standing crops 
and environmental variables. For example, fish 
standing crop in Bull Shoals Lake has been 
positively related to the volume of water flowing 
into the lake during the period January-July. 
Defining the factors which influence fish production 
in reservoirs and quantifying these relations is 
essential to effective fishery management. Cove 
sample data are also being used to measure 
variations in spawning success of many fish species, 

Male black crappie guarding nest of eggs in adventitious 
roots on trunk of flooded willow tree in Bull Shoals Lake. 
Photos by L. E. Vogele. 

to monitor long-term changes in the adult 
populations, and to define relations between 
predators and available prey and evaluate the 
adequacy of the food base. 



<9 Ui 

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z o 


CO o 



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-5 * 


4 uj 

3 £ 

-2 5 

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Standing crop of fish in Bull Shoals Lake, as estimated by 
cove rotenone sampling, and total inflow for the period 
January-July, 1968-76. 

Feeding and Behavior of Largemouth Bass Fry. 
— In a study of the diel activity and feeding of 
schooled largemouth bass fry, a school of fry was 
observed and a sample of fry collected for stomach 
content analysis at 3-hour intervals for 24 hours. 
During most of the day, the location and 
configuration of the school changed little, and the 
fry fed continuously on limnetic zooplankters. Fry 
did not feed at night but remained inactive and 
closely aggregated in one location. 

Abundance of Black Basses Estimated by 
Electrofishing. — Annual estimates of black basses 
in Beaver and Bull Shoals lakes provide a means of 
assessing long-term production and mortality and 
serve as a means of evaluating the effects of angler 
harvest. Mark-and-recapture estimates are made 
along selected sections of shoreline of each 
reservoir in the spring. In Beaver Lake, the 
estimated 1976 bass population (number per 
kilometer of shoreline) in the standard (downlake) 
study area used since 1968 was 39 for largemouth 
bass and 128 for spotted bass. This was the lowest 
estimate of largemouth bass density and the first 
reliable estimate of spotted bass density since the 
study began. In a second study area (mid-lake) in 
Beaver Lake, the largemouth bass population was 
estimated at 162/km, which was a marked 
decrease from 275 in 1975. In Bull Shoals Lake, the 
estimate of largemouth bass abundance was 87/ km 
of shoreline, a more than twofold increase over the 
1975 estimate. No reliable estimates of spotted or 
smallmouth bass were obtained. 

Abundance and Survival of Young Black Bass in 
Beaver Lake. — Young black bass were sampled at 
frequent intervals in Coose Creek on Beaver Lake 
during June-August 1976, as part of an evaluation 
of factors influencing abundance, growth, and 
survival. Abundance of young largemouth and 

spotted bass was estimated at the schooling fry 
stage and at various intervals through early August. 
After the schools broke up in early June, the two 
species were about equally abundant. A much 
higher rate of mortality of largemouth bass through 
early August, however, resulted in a marked shift in 
relative species abundance. Earlier studies on 
White River impoundments suggest that spotted 
bass are more successful than largemouth bass 
during years such as 1976, when little or no 
shoreline vegetation is flooded during the summer. 

Cooperative Predator-Stocking Evaluation. — 
Physicochemical and fish standing crop data from 
26 southern reservoirs were analyzed as part of a 
predator-stocking evaluation conducted under the 
auspices of the Reservoir Committee of the 
Southern Division of the American Fisheries 
Society. Correlation and regression analyses were 
used to locate and quantify relations between 
selected reservoir environmental variables and fish 
standing crops. Water-flow related variables (e.g., 
outflow, volume, and storage ratio), dissolved 
solids, and length of growing season were generally 
closely correlated with fish standing crops. High 
volumes of inflow and increased water exchange 
rates were associated with increases in fish standing 
crop and changes in the size structure of fish 
communities in several of the reservoirs. 

Angler Use and Harvest. — Estimates of angler 
use and harvest have been an integral part of the 
fishery studies on White River impoundments. Use 
and sport fish harvest have decreased markedly 
since impoundment. Data collected during the past 
1 1 years have been integrated into a time series 
study that will ultimately permit prediction of use 
and harvest on the basis of environmental variables 
(e.g., temperature, conductance, transparency, 
water inflow, and surface area). 

Analysis of data from a 3-year study of the Bull 
Shoals tailwater put-and-take rainbow trout 
fishery indicated an efficient harvest of trout (more 
than 90% of the fish stocked) during the years of 
low water release. During sustained periods of high 
tailwater flow, however, both effort and harvest 
dropped precipitously — though mean size of the 
trout caught increased substantially. 

Multi-outlet Reservoir Studies in DeGray Lake. 
— In limnological and population dynamics 
research on multi-outlet DeGray Lake, we 
continued to develop data bases on the fishery 
during a period when the water is being released 
from the epilimnion, for comparison with data for a 
future period when it will be released from the 
hypolimnion, and to provide data to the Corps of 






cc 30 




-I 1 1 1 1 1 >~ 

"T 1 1 1" 



1964 - 1975 

12-year mean ® 




4 6 8 10 12 14 16 18 20 

Annual sport fish harvest, Beaver Lake, 1964-75, with plots 
of the 1 2-year mean of 21 .3 pounds per acre, and predicted 
harvest (Formula E, National Reservoir Research Program 
formula compilation, June 1974. Mimeo, 11 pp.). Harvest 
estimates do not include night fishing. 

Engineers, Waterways Experiment Station, for 
development of physical and mathematical models 
of DeGray Lake. 

Largemouth bass population estimates in 
DeGray Lake were completed during the spring of 
1976 to establish biomass level of the principal 
predator. The lakewide average of 459 bass/ km of 
shoreline was 6 km less than the 1975 average. Age 
and size composition determined for 1,898 bass 
captured in 1975 indicated that 61% of the 
estimated number and 10% of the weight was 
composed of 1-year-old (1974 year class) bass less 
than 250 mm long. Bass of the 1966-68 year classes 
(hatched before impoundment) made up only 2.3% 
of the numbers and 12% of the weight. 

Cove sampling with rotenone in August of each 
year since 1974 indicated that total fish biomass of 
DeGray Lake has decreased each year. Standing 
crop estimates (kg/ha) averaged 416 in 1974, 248 in 
1975, and 186 in 1976. Although declines in the 
standing crop estimates were noted for most species 
in 1976, reduction in the biomass of adult gizzard 
shad accounted for much of the decrease. Biomass 
estimates for bluegills, crappies, and channel 
catfish declined in 1976, but the estimated mean 
crop of largemouth bass was 16.4 kg/ ha in 1976 as 
compared with 13.1 kg/ha in 1975. Reproductive 
success of largemouth bass increased in 1976, with a 
lakewide average of 519 young-of-the-year per 

hectare, compared with 304 in 1975. 

Twelve biweekly collections of centrarchids were 
made beginning in April 1976 to define food habits 
for modeling purposes. Largemouth bass stomachs 
contained shad, centrarchids, steelcolor shiners, 
brook silversides, frogs, crayfish, and (in stomachs 
of the smaller bass) a few aquatic insects. Analyses 
of the stomach contents of other centrarchids are 

Mid-water trawling is being used to estimate 
population size and production of pelagic larval 
fish in DeGray Lake. The principal species are the 
threadfin shad, gizzard shad, black crappie, white 
crappie, and sunfishes (Lepomis). Bimonthly 
estimates were made from May through September 
1975 and 1976. Catches of threadfin shad, the most 
abundant larval species, increased in 1976. Perhaps 
as a result of higher than normal spring water 
temperatures, peak catches occurred during the 3rd 
week in May 1976, 2 weeks earlier than in 1975. The 
1975 threadfin production was about 7 kg/ ha. 

Larval fish loss in discharge from a power- 
generation plant was also studied. Because the 
bottom of the present outlet of DeGray Lake acts as 
a weir and coincides with the top of the thermocline 
at normal water levels, most of the water discharged 
comes from the epilimnion. During most years, 
high discharge volumes will coincide with peak 
larval fish abundance in the epilimnion during May 
and June. Weekly 1-m net samples were taken 
below the dam from April through August. 
Numbers of larval fish collected reached a peak of 
0.79/ m 3 of discharge water in May 1975, and 
1.42/m 3 in May 1976. Total water volumes 
discharged during May and June were 220.4 million 
cubic meters in 1975 and 91.6 million cubic meters 
in 1976. Estimated larval losses during these 2 
months were 153.2 million in 1975 and 72.1 million 
in 1976. 


Effect of Thermal Discharges on Fish. — Addition 
of heated water to the environment from the 
increasing number of nuclear fuel and fossil fuel 
steam-electric plants has caused much concern 
among aquatic biologists. Water temperature 
regulates the rate of all life processes for fish and 
other cold-blooded aquatic life, and changes caused 
by power plant discharges can have both 
detrimental and beneficial effects. Recent trends in 
constructing pumped-storage hydroelectric power 
plants have placed additional unknown stresses on 


aquatic communities. In pumped-storage projects, 
electricity is generated during hours of peak 
electrical need; during hours of reduced power 
needs, water is pumped back into the reservoir for 
reuse during the next period of peak power 
generation. Rapid water-level fluctuation, strong 
currents, and marked water temperature changes 
are usually associated with this operation. There 
now are about 22 pumped-storage plants in 
operation and over 1,000 potential pumped-storage 
sites have been identified in the United States. 

Southeast Reservoir Investigations was established 
in 1972 to evaluate long-term effects of thermal 
discharges from steam electrical generating plants 
and pumped-storage hydroelectric plants on fish 
and other aquatic life in reservoirs. Research to 
date has been in Keowee (18,000 acres) and 
Jocassee (7,500 acres) reservoirs in northwestern 
South Carolina. Keowee Reservoir is the source of 
cooling water for Oconee Nuclear Station, and 
hydroelectric power is generated at Keowee Dam. 
Keowee is the lower reservoir and Jocassee the 
upper reservoir of a pumped-storage hyrdoelectric 
plant. Additional pumped-storage facilities are 
planned, in which Jocassee will be used as the lower 

Fish populations in Keowee and Jocassee 
reservoirs are sampled with trawls, seines, gill nets, 
electroshocker, and rotenone to measure changes in 
composition and abundance of fish species and to 
collect life history information. Plankton and 
bottom-dwelling animals are sampled seasonally by 
standard methods. Water-quality data are collected 
to describe environmental changes caused by power 
plant operations. Sampling methods and locations 
have been standardized so that results can be 
compared between areas each year. A creel census 
conducted in cooperation with the South Carolina 
Wildlife and Marine Resources Department 
documents angler use and harvest in the two 

Data analyzed identify changes in aquatic life 
that occurred in response to changing environmental 
conditions while the reservoirs were filling; during 
the early years after the reservoirs filled, before 
power plant operations; and during the periods 
when the plants went into production. The three 
reactors at the Oconee Nuclear Station became 
fully operational in early 1975 and all four pump 
turbines at Jocassee Dam were operable in mid- 
1975. Data showing the long-term, possibly subtle, 
effects of these power plants are not yet available. 
However, some effects of these power plants are 
becoming obvious. 

Since 1971 there have been significant changes in 
the water temperature of Keowee Reservoir. 
Average annual weighted (by volume) temperature 
at all stations was 12.9° C in 1971 and 17.6° C in 
1975. Results from the first 8 months of 1976 closely 
parallel those for 1 975, suggesting that the reservoir 
may be reaching the maximum temperature likely 
to occur under the current operating capacity of the 
nuclear power plant. The reservoir warms earlier 
than normal in the spring, resulting in earlier 
spawning of fish and earlier emergence of midge 

Water temperatures at 15 m were closely 
correlated with percent operating capacity of the 
nuclear plant, whereas temperatures at 1 m were 
generally correlated with the weather. Since the 
plant has been in operation, the depth of the 
thermocline during summer has been progressively 
depressed. As a result, temperatures at 20 m during 
late summer have increased 13° C over pre- 
operational levels. From September to April, when 
the plant is operating at 80-90% of capacity, a 
thermal plume in which temperatures are l°-5° C 
above natural temperatures extends from the 
surface to a depth of 16-18 m and covers about 20% 
of the reservoir. 

Jocassee Reservoir also exhibited considerable 
temperature changes since all pumping units went 
into operation. The reversible turbines move warm 
water from Keowee Reservoir up 300 feet into 
Jocassee Reservoir. Influence of this added heat is 
of particular interest because a "two-story" trophy 
trout fishery was established in the reservoir by the 
South Carolina Wildlife and Marine Resources 
Department in late 1973. At this latitude trout in 
reservoirs are restricted to cool, well-oxygenated 
waters of the thermocline during summer. Adding 
heated water from Keowee has shifted the upper 
limits of the trout habitat downward in late 
summer. Since the water of Jocassee Reservoir 
usually does not mix completely in the fall, there is 
little or no oxygen at the greater depths, thus 
resulting in further reduction of trout habitat. 
There has been a net loss of about 25% in summer 
trout habitat since 1973. 

Effects of habitat alterations on organisms near 
the bottom of the food chain are difficult to 
measure and evaluate, but the information is 
essential to understanding changes occurring 
throughout the aquatic community. Zooplankton 
densities decreased 43% between 1973-74 and 1974- 
75 and remained stable into 1975-76. These 
changing values are more closely related to the 
standing crop of threadfin shad (the major 


planktivore) than to the level of power plant 
operation. A large decrease in planktonic larvae of 
phantom midges (Chaoborus) during this time also 
appears related to shad abundance. 

Entrainment of zooplankton in the cooling water 
supply is limited to July, August, and September. 
Mortality from passage through the plant appears 
to be small. Maximum temperatures have not 
reached levels lethal to zooplankton. 

Zooplankton species composition throughout 
the reservoir has remained stable, except for 
Daphnia laevis, which was common in 1973, absent 
in 1974 and 1975, and reappeared in 1976. Overall, 
the operation of Oconee Nuclear Station has had 
no marked effect on zooplankton to date. Likewise, 
the power plant appears to have had no major effect 
on the abundance and species composition of 
benthic organisms. 

Changes in feeding, growth, and reproductive 
success of fishes usually occur after water 
temperature changes or other habitat modifications. 
Consequently the life histories of four major game 
fishes in Keowee Reservoir have been followed 
since the laboratory was established. Estimates 
based on scale samples indicate that growth rates of 
bluegills and yellow perch have remained nearly 
constant since 1972. However, growth of black 
crappies and largemouth bass appears to have 
increased. After plant operations began, the 
weights of adult bass were nearly double those of 
fish of the same age collected in earlier, years. 

Interpretation of the growth changes of black 
crappies and bass is difficult because the reservoir 
was stocked with threadfin shad as a prey species at 
about the same time the power plant began 
operation. Examination of bass stomachs indicated 
that bass fed heavily on threadfin shad during the 
summers of 1974 and 1975. 

Stomachs from young-of-the-year black crappies 
(5 to 22 mm long) and yellow perch (6 to 30 mm 
long) contained only zooplankton before heated 
water was added to the reservoir. Zooplankton and 
immature aquatic insects made up most of the diet 
of adult black crappies (130 to 239 mm long) and 
zooplankton most of the diet of adult yellow perch 
(to 300 mm long). These early observations stress 
the need for understanding changes which occur at 
all levels of the food chain. 

To determine time and success of spawning and 
develop estimates of relative abundance, growth 
rates, and mortality of young fish (4 to 30 mm long), 
we operated experimental fine-mesh trawls (one 
with 0.8-mm mesh openings and one with 2.5-mm 
mesh) from March through September in both 

reservoirs. Trawl catches of yellow perch, black 
crappies, and sunfish were highest in 1973 and 
declined progressively through 1975 as heated 
water was added to Keowee Reservoir. All 
remained low in 1976 except for the black crappie, 
which returned to the 1974 catch level. Catches 
were lowest near the heated water discharge after 
the plant began operating. No trends or changes in 
abundance of larval fishes are now discernible in 
Jocassee Reservoir. 

Threadfin shad were stocked by the State in 1973 
in Jocassee Reservoir and in Keowee Reservoir in 
1974 to provide additional food for predatory 
species. They have reproduced and now make up an 
important part of the trawl catches in both 

Fish are sampled in coves (by application of 
rotenone) annually in both reservoirs to provide 
estimates of species and size composition of the 
nearshore fish population. In general, no major 
changes have occurred since the power plants began 
to operate. Reduction of larval yellow perch and 
sunfish, suggested by trawling, have not been 
detected in the cove samples. Data for crappies, 
however, correspond with those from the trawls: 
numbers were reduced in 1976 samples. 

Recent samples show that Keowee Reservoir 
contains about 50 pounds of fish per acre and 
Jocassee Reservoir about 30 pounds. Largemouth 
bass contribute 4 pounds per acre to Keowee 
Reservoir and 6 pounds to Joccassee. 


Striped Bass Nutrition. — We completed the final 
two of nine feeding trials begun in 1975 to define 
several nutritional requirements of striped bass 
fingerlings in intensive culture. Data were 
assembled, reduced, and analyzed statistically for 
information on optimal protein and lipid content in 
synthetic diets, feeding rates, and stocking rates in 
tank culture so that a more complete description of 
a least-cost diet can be used in ration formulations 
for production. The following protein (casein) 
contents should yield the following respective 
growth rates (g/day per fingerling): 32%, 0.184; 
34%, 0.210; 36%, 0.234; 38%, 0.244; 43.5%, 0.247; 
and 49%, 0.250. 

Feeding rates with optimal protein level (38% 
casein) may be selected in consideration of the 
following conversions: 1% (dry diet) of body weight 
per day yielded 0.126 g flesh per day per fish; 2% 
yielded 0.225 g; and 3%, 0.245 g. Conversion 


efficiency was 2.4, 2.9, and 3.8, respectively. 

Data on lipid requirements are not complete but 
growth rates in short-term feeding trials were 
linearly proportional to lipid contents in diets 
containing 0-6% salmon oil (6% is the highest 
content tested thus far). 

The difficult problem of developing acceptable 
larval foods is still given high priority. We tested 
several "whole" foods on hatchling striped bass, 
both with and without initial feeding of live brine 
shrimp nauplii or Daphnia, and with several 
methods of application. The foods were prepared 
from eggs, frozen brine shrimp, beef liver, canned 
mackerel, casein-base diet, or ground Ewos Trout 
Starter (after gelling with agar or gelatin, drying, 
and sizing to 50-100 ;um), along with commercial 
microencapsulated food. None of these feeds 
proved successful for production use, but the 
results gave us a better understanding and 
definition of problems with larval foods to help 
design future studies. 

Largemouth Bass Nutrition. — We completed 
the final two of seven feeding trials begun in 1975 to 
define nutritional and related factors in tank 
culture of largemouth bass. Results of these tests 
provide guidelines for protein and lipid content in 
least-cost maintenance and production rations for 
fingerling bass. Protein content of 36% gave best 
growth (contents of 32 to 38% were tested). In 
earlier trials, protein up to 54.5% did not improve 
growth over that given by 38%. Diets containing 6% 
salmon oil (0 to 6% tested) gave best gains; 4.5% 
and less appeared to be limiting. 

Channel Catfish Tail Abnormalities. — Abnormal 
tails that developed in up to 16% of the catfish fry in 
different lots range from complete club tail to 
partial tail development. A pilot survey of 17 lots of 
catfish fry with the same general history had 
ascorbate levels in eggs ranging from 4 to 20^g/g 
(fresh weight). A statistical correlation was not 
possible because too few samples were available to 
make a valid test, but the highest incidences of 
abnormal fry developed from eggs having less than 
6 jug ascorbate per gram (fresh weight) of eggs. A 
few brood stock fish with short, stubby tails also 
had eggs in which ascorbate values were low. 
Inasmuch as short-tail males crossed with normal 
females yielded normal fry, a "cytogenetic" effect is 
apparent. Too little information is as yet available 
to judge whether this condition resulted from a 
deficiency in vitamin C metabolism, a condition 
that might be caused by long-term exposure to 
organochlorine residues, inbreeding, or other 

Tail deformities occur in up to 16% of the channel catfish 
developed from eggs with low ascorbate levels (normal, 
upper right). The possible causes of this "cytogenetic" 
effect being investigated include diurnal low dissolved 
oxygen, poor water quality, temperature effects, and 
inadequacy of the brood stock — perhaps resulting from 
diet deficiency during egg development, from inbreeding, 
or from exposure to pesticides. Photo by B. F. Grant. 


The Energetic Efficiency of Fish. — Fish are more 
efficient in converting food energy into body 
growth than are other domestic animals. This fact 
was confirmed by experiments which directly 
measured the heat produced by living fish. Feed 
which is digested and absorbed either appears as 
growth of the animal or is used to supply energy and 
appears as heat. Measurement of the heat produced 
gives an indication of energetic efficiency. 

It was found that fish are much more efficient in 
metabolizing protein than are other animals. 
Warm-blooded animals lose as much as 30% of the 
energy of protein as extra heat production after a 
high protein meal. This loss in rainbow trout was 
less than 10%; thus more of the energy in the feed 
was available for growth and less was used for heat 

Brood Stock Nutrition. — Diets for brood stock 
cutthroat trout in hatcheries have been, at best, only 
moderately successful. Therefore, a cooperative pilot 
study was undertaken with the Fish Cultural Center 
in Montana to obtain basic chemical data on eggs 
from various hatchery and wild trout. The results 
obtained provide a sound basis for formulating 
diets better balanced in essential amino acids, 


which are the vital components of protein. 

Prevention of Cataracts Induced by Whitefish 
Meal. — Rainbow trout fed whitefish meal as a 
source of protein develop lens cataracts; however, 
cataract formation can be completely and 
economically prevented by dietary supplementation 
with a newly developed practical mixture of 
essential minerals that also improve growth and 
feed conversion. 

Influence of Water Temperature and Ammonia 
on Ionic Regulation of Trout in Closed Systems. — 
Under conditions of complete water reuse, the 
toxicity to salmonids of nitrogenous metabolic 
wastes (ammonia, nitrate, and nitrite) in culture 
water has routinely been found to be less than that 
in either flow-through culture systems or reuse 
systems in which water is periodically replaced for 
waste flushing. Retaining 100% of the culture water 
in recirculation conserves essential nutrients for the 
organisms in the biofilter that purify the water 
through their metabolic activity; performance is 
further improved by adding nutrients (inorganic 
carbon and calcium) to the culture water for use by 
the filter organisms. It is believed that increased 
numbers and metabolism of the purifying bacteria 
in closed-circuit culture systems contribute toward 
reducing the toxic effects of nitrogenous wastes at 
the higher measured concentrations through 
sequestration in, or modification by, the retained 
biofilter organisms. A practical 100% water reuse 
system for salmonid culture can be significantly 
smaller than one which wastes filter organisms and 
nutrients with each discharge of culture water 
during a dilution cycle. 

Stability and Efficiency of Vitamin C and 
Vitamin C-sulfate in Rainbow Trout Diets. — 
Chemical studies conducted to measure the 
stability of conventional vitamin C (C) in fish diets 
stored for 1 and 3 months at room temperature 
showed 70 and 98% decomposition. In contrast, 
results for vitamin C-sulfate (C-S0 4 ) stored for 3 
months at room temperature and at 1 1 3° F showed 
losses of less than 20 and 30%, respectively. 

Quantitative nutritional experiments showed 
that C-S0 4 was as effective as C, on a molecule-to- 
molecule basis, in preventing deficiencies in trout, 
and that the minimum dietary requirement was 
considerably lower than indicated in the literature. 

Heat-treated Full-fat Soybeans for Rainbow 
Trout. — Satisfactory growth and health were 
obtained in trout fed heated full-fat soybeans in 
starter diets containing only 10% fish meal and in 
grower diets containing none. Growth of trout and 
level of an antinutritional factor correlated with the 

degree of heat treatment of the soybeans. 

Vitamin D Requirements of Fish. — Reports on 
the nutritional role of vitamin D vary because of 
differences in dietary ingredients, level of calcium, 
form of the vitamin studied, and species or age of 
fish. The requirement needs to be clarified. Two 
experiments with rainbow trout indicated smaller 
growth responses (ca. 10%) to supplements of 
vitamin D and calcium that were related to the type 
of diet. There appeared to be no vitamin X calcium 

Feed Use as Affected by Growth Stimulants. — 
Several feed additives, some of which are used to 
promote growth in swine, poultry, and cattle were 
tested for their ability to stimulate trout growth. 
None of the compounds tested, however, improved 
growth rate. Five of the agents markedly depressed 
liver size (by 40%) and one — stilbestrol — retarded 
growth rate, increased liver size, caused liver 
degeneration, and decreased liver glycogen by 70%. 


New Vaccine Delivery System. — In a continuing 
effort to improve protection offish by immunization, 
the Western Fish Disease Laboratory, working 
cooperatively with Wildlife Vaccines, Inc., Denver, 
Colorado, has developed a method to immunize 
large numbers of fish in a safe, expeditious, 
effective, and economic manner. We found that fish 
would take up large quantities of vaccine if they 
were placed in a hyperosmotic solution for about 2 
minutes and then transferred to the vaccine for 
about 3 minutes. Five variables were found to be 
important: antigentic mass, type and concentration 
of the hyperosmotic solution, pH, duration of 
exposure, and temperature. 

The vaccine solution does not enter the fish 
through the mouth. Some vaccine enters through 
the gills, but the major portal of entry is the lateral 
line. The association of the lymphatic system with 
the lateral line may explain the effectivenes of this 
vaccination method. We have successfully immunized 
salmonids to enteric redmouth disease, Vibrio 
anguillarum, and infectious hematopoietic necrosis 
virus using this procedure. Although the method 
was developed primarily for the delivery of vaccines 
to fish, it perhaps could be used for administering 
chemotherapeutics, markers, essential nutrients, or 
other substances difficult to administer to large 
numbers of fish, especially when the oral route 
cannot be used. 


Toxicity of Nitrate to Developing Trout Eggs. — 

Inasmuch as intensive agricultural practices are 
known to result in high nitrate levels in ground- 
water supplies used by hatcheries, we carried out a 
study to determine whether nitrate levels commonly 
found in some groundwater inhibits normal 
development and hatching of trout eggs. Groups of 
eyed rainbow trout eggs were exposed to levels up 
to 20 ppm nitrate for 2 weeks before and 4 weeks 
after hatching. The exposure of eggs and fry for this 
6-week period caused statistically significant 
increases in egg mortality at 20 ppm and in the 
frequency of abnormalities in fry hatched from eggs 
exposed to concentrations of 5 ppm or higher. In 
addition, a subjective observation was that many of 
the fry being exposed to 20 ppm appeared lifeless 
and often were mistaken for mortalities until reflex 
movement was shown when the fish were disturbed. 
Ozone Toxicity to Fish. — The toxicity of ozone 
to fish must be determined before recommendations 
can be made for the use of this chemical to disinfect 
water supplies or as a replacement biocide for 
chlorine. To obtain this information, we exposed 
juvenile rainbow trout (average weight, 15 g) to 
dissolved ozone up to 0.002 ppm in a continuous- 
flow system. Ozone was toxic to rainbow trout 
(estimated 96-hour LC50, 0.004 ppm ozone). 
Subjectively, fish exposed to the two highest ozone 
concentrations showed increased respiration rate 
and "coughing" frequency, and the gills became 
pale. Loss of equilibrium often preceded death by 
several hours, as it commonly does when fish are 
exposed to toxicants. Fish exposed to ozone at the 
two highest levels suffered relatively severe blood 
chemistry disturbances, characterized by high 
blood sugar and abnormally low sodium and 

chloride levels. Examination of circulatory blood 
smears stained with Leishman-Giemsa indicated 
significant decreases in lymphocytes and increases 
in neutrophiles and immature erythrocytes, at all 
ozone levels. The Leishman-Giemsa stained kidney 
imprints showed no apparent morphological 
change. Histologically, the gill epithelium of some 
fish exhibited severe hyperplasia and some 
epithelial separation. Many of the hyperplastic 
areas were extensive enough to cause "clubbing" of 
the lamellae and the filaments. 

Screening of Chemicals for Disease Treatment. 

— There is a continuous need to identify chemicals 
that have potential value for treatment of fish 
diseases — especially virus diseases. 

The virucidal properties of iodine, chlorine, 
formalin, thimerosal, malachite green, and 
acriflavine were tested against infectious pancreatic 
necrosis virus. Iodine and chlorine showed good 
activity, but efficacy depended on the concentration 
of virus, presence of organic matter (calf serum), 
and water pH. Water hardness (0-300 ppm as 
CaC0 3 ) did not affect virucidal activity. The 
addition of 0.5% calf serum significantly reduced 
iodine concentration and virucidal activity. 
However, the addition of only 0.07% serum greatly 
reduced the chlorine concentration and the 
virucidal contact time was extended to 30 minutes. 

A 60-minute exposure of the virus to 0.2% 
formalin failed to inactivate all virus. Thimerosal at 
0.2% in 10 minutes and malachite green at 5 mg/1 
for 60 minutes also failed. Acriflavine at 500 mg/1 
for 20 minutes failed to inactivate the virus, but at 
0.5 mg/1 in cell culture media it prevented the 
development of cytopathology. 

Migratory Birds 


Satellite Imagery Predicts Productivity Among 
Arctic-nesting Geese. — Arctic breeding grounds of 
North America supply most of the geese available 
to hunters in Canada, the United States, and 

Mexico. Brant and snow geese breed only in the 
Arctic, and large segments of Canada goose 
populations breed there. Successful reproduction 
of geese in this region is dependent upon timely 
disappearance of ice and snow. The nesting and 
brood-rearing periods are short, and the opportunity 
for renesting or even nesting at all is greatly 


curtailed if conditons are not favorable. In fact, the 
productivity of arctic geese is highly variable 
because of annual changes in breeding habitat 
conditions. In one year, the birds may be quite 
successful; the next year may bring virtually 
complete failure. In the past, the likely reproductive 
success of the birds unfortunately could not be 
determined in time to set appropriate hunting 
regulations. The region occupied by the birds is so 
large and so remote that aerial and ground censuses 
are not economically feasible. Earth-orbiting 
satellites have provided a means of predicting 
probable annual productivity based on presence or 
absence of extensive snow cover during June, a key 
period in the breeding season. 

Interpretations of satellite imagery in 1973, 1974, 
and 1975 agreed well with later information 
gathered from counts of young in goose flocks and 
from the measured ratio of young to adults in the 
harvest. During the first 2 years, breeding 
conditions were poor and reproduction was very 
low. In contrast, satellite imagery in 1975 revealed 
much better habitat conditions. Breeding success 
that year proved to be much higher. Satellite 
imagery is not infallible — for example, nest losses 
caused by sudden storm tides cannot be detected. 
Nevertheless, this space-age tool has proved to be a 
valuable means of measuring "boom" and "bust" 
years in time to make appropriate adjustments in 
hunting regulations in the management of this 
important resource. Development of this monitoring 
technique resulted from cooperative efforts of the 
Service's Office of Migratory Bird Management, 
the Migratory Bird and Habitat Research 
Laboratory, and the Canadian Wildlife Service. 

Research on Shore and Upland Game Birds 
Continues. — The accelerated Research Program 
for Migratory Shore and Upland Game Birds is to 
develop effective management plans for this highly 
important group of birds. Each year, $175,000 is 
contracted to States and universities for much- 
needed research on a wide variety of birds, 
including mourning and white-winged doves, band- 
tailed pigeons, woodcock, snipe, and rails. Of 32 
studies now in progress, 9 are being conducted by 
State Conservation Departments, 18 by universities, 
and 5 by Cooperative Wildlife Research Units 
(Louisiana, Missouri, Oklahoma, Pennsylvania, 
and Wisconsin). 

The Colorado Division of Wildlife gathered new 
information on breeding cycles of band-tailed 
pigeons. These pigeons respond not only to photo- 
periodicity but also to other environmental cues, 
especially food availability. If food is scarce, 

pigeons may wander until they find adequate 
provisions. On occasion, the birds will react to 
unusually good acorn crops and nest for a 
protracted period of time. An abundance of food 
may account for reports of fall and winter nesting. 

A mourning dove study in Oklahoma indicated 
that biologists should be cautious in using primary 
feathers and their coverts to backdate and estimate 
dates of hatch. Indications of delayed molt were 
apparent in 26% of a sample of 76 young doves. The 
delayed molt was observed among birds trapped 
during the winter and probably was due to harsh 
weather and limited food. 

In Pennsylvania, an informative study has 
provided insight into some of the details concerning 
fall migration of woodcock. Onset of migration of 
nine radio-marked birds occurred between 
November 30 and December 9, 1973, and between 
November 18 and 29 in 1974. Departures coincided 
with high-pressure centers approaching from the 
north and west or low-pressure centers retreating to 
the north and east. Eight of nine woodcock 
departed 2.5 or more hours after sunset and at least 
seven of the nine left before midnight. Two birds 
were tracked by aircraft 125 miles SSW of the study 
area during two nights. Air speed of the birds was 
22 and 28 mph. The birds flew only at night and 
followed a river system extending south into 
Maryland and Virginia. Local birds were among 
the last to leave; most woodcock from more 
northerly regions had already migrated from the 
area. Temperatures at or near freezing, accompanied 
by favorable winds, appeared to stimulate 
migratory flights. Findings of a Virginia woodcock 
study suggest that woodcock may nest more 
frequently in southern States than had been 
believed. Research by the Virginia Game and 
Inland Fisheries Commission has revealed that 
male woodcock "peent" in the northeastern portion 
of the State from mid-February to mid-June, with a 
peak of calling activity in late February. Nests have 
been located throughout most of the State, with the 
exception of the region west of the Blue Ridge 
Mountains. Most nests were found in March and 
April; the peak of hatch probably occurs in early to 
mid-April. The extent of woodcock breeding in the 
South has become an important question in 
woodcock management, and much additional 
research is needed to determine methods of 
measuring the contribution of southern breeding 
habitat(s) to rangewide woodcock productivity. 

Ingested Lead Shot High Among Sora Rails in 
Maryland. — The incidence and adverse effects of 
ingested lead shot are well known for most 


waterfowl. However, the magnitude of this 
problem for other groups of birds is not adequately 
understood. Sora rails are hunted in both inland 
and coastal marshes. A cooperative effort between 
the Migratory Bird and Habitat Research 
Laboratory and the Missouri Conservation 
Department documented the incidence of lead 
pellets in the gizzards of 934 soras shot in Maryland 
and Missouri. Ingested shot was found in 12.3% of 
the Maryland birds but in only 1.8% of the Missouri 
sample. Individual birds from Maryland marshes 
had ingested up to 28 pellets. None of the pellets 
was larger than No. l x /i shot. These findings 
suggest that lead poisoning may be an important 
cause of loss in sora rails, especially in Maryland. 

Nesting Ospreys Counted in the Coastal 
Carolinas. — An aerial census, coupled with several 
intensive ground counts, was initiated in 1973 to 
determine distribution and abundance of ospreys. 
Counts were made in Chesapeake Bay in 1973 and 
were expanded in 1974 to include the coastal 
portions of North and South Carolina. An 
estimated 1,450 ± 44 pairs nested in Chesapeake 
Bay in 1973 and 571 ±34 pairs were in the coastal 
Carolinas in 1974. Evidence from several small 
intensive study areas suggest little or no change in 
abundance during the past few decades. The high 
degree of successful nesting on a variety of man- 
made structures, such as navigational buoys in the 
Bay, together with heavy use of altered habitat in 
the Carolinas, indicates that the osprey is quite 
adaptable. The success of this initial research 
indicates that trends in osprey populations may be 
monitored accurately by using a twofold approach 
— aerial surveys to measure abundance, and 
ground studies to correct for birds unobserved from 
airplanes and to measure reproductive success. 
Results of the research suggest also that ospreys 
along the middle and south Atlantic coast are faring 
better than had been believed. 

Breeding Bird Survey (BBS) Documents Range 
Expansions. — The BBS, a cooperative program 
sponsored jointly by the U.S. Fish and Wildlife 
Service and the Canadian Wildlife Service, is now 
in its 1 1 th year of measuring changes in distribution 
and abundance of nesting birds in North America. 
Each summer, skilled bird watchers and their 
assistants, who help with the map reading, driving, 
and recording, arise 1 to 3 hours before sunup and 
drive to the starting points of some 1,800 randomly 
located survey routes. At exactly 30 minutes before 
sunrise each observer begins the first of 50 3-minute 
counts along a 24.5-mile transect. The resulting 
tallies are edited in the Migratory Bird and Habitat 

Research Laboratory, then digested by computer to 
see which species are increasing and which are 
decreasing, and where these changes are occurring. 
Few species are expanding their breeding ranges 
as dramatically as the barn swallow in North 
America. The 150-mile southward extension of 
range throughout the southeastern and south- 
central States that occurred between 1966 and 1973 
appears to be continuing. Because it measures 
relative density of birds as well as their presence or 
absence, the BBS also shows that as the range has 
expanded, so have the areas of greater density. The 
Survey also indicates that other species are 
extending their ranges. Populations of the cattle 
egret, an invading species, are still increasing 
rapidly in the East. 

Invasion of the southeastern States by nesting barn 
swallows. Breeding Bird Survey data show southern limits 
of breeding range in 1966 and in 1973. 


Use of Laboratory Heavy During Its First Year of 
Existence. — From July 1, 1975, through 
September 15, 1976, a total of 1,219 birds, 16 
mammals, 1 salamander, and 2 fish were submitted 
for necropsy to the Service's newly formed National 
Fish and Wildlife Health Laboratory. In addition, 
more than 2,000 bird necropsies were conducted in 


the field by Laboratory personnel. Tissues from 577 
other birds and 6 other mammals were also 
submitted to the Laboratory for testing, along with 
21 bird eggs, 142 fecal samples, and 29 other 
samples. Birds examined varied in size from a 
hummingbird that died from aspergillosis to a 
sandhill crane that died from lead poisoning. 

The most common findings were avian cholera, 
lead poisoning, avian botulism, salmonellosis, and 
aspergillosis. Pasteurella multocida, the causative 
agent of avian cholera, was isolated from 20 species 
of migratory birds and from all four flyways. 
Included were 10 species of ducks, 4 species of 
geese, whistling swan, eared grebe, California gull, 
little blue heron, sandhill crane, and snowy owl. 

For the second consecutive spring, avian cholera 
erupted in the Rainwater Basin of south-central 
Nebraska. This important waterfowl staging area 
concentrates most of the midcontinent's population 
of white-fronted geese and is also frequently used as 
a stopping area by whooping cranes. During the 
avian cholera epizootic of 1975, approximately 
35% of the loss of 15,000 to 20,000 waterfowl 
involved white-fronted geese. Nine whooping 
cranes had to be hazed from the area during the 
height of this outbreak to protect them from avian 
cholera. Approximately 10% of the 7,000 to 8,000 
birds lost to avian cholera during the spring of 1976 
were white-fronted geese. Other heavy losses of 
waterfowl from avian cholera occurred in 
California and South Dakota during that year. 

Avian botulism was widespread, with the 
heaviest losses occurring in California, New 
Mexico, Illinois, Utah, and Minnesota. Other 
botulism die-offs, due to Clostridium botulinum 
type C, occurred in Montana, Texas, Oregon, 
Massachusetts, Wisconsin, North Dakota, Indiana 
Maryland, Nevada, Virginia, North Carolina, 
Idaho, Washington, Colorado; also Ontario, 

Losses from lead poisoning were also detected in 
all four flyways; the greatest number of losses 
involved snow geese from South Dakota, whistling 
swans in North Carolina, and a variety of ducks in 

Erysipelas Kills Eared Grebes in Utah. — It was 
estimated that 5,000 migrating eared grebes, 
apparently caught in a heavy snowstorm on Great 
Salt Lake on November 26, 1975, died of what was 
diagnosed at the Bear River Research Station as 
erysipelas, probably aggravated by weather- 
induced stress. A few ducks and gulls were also 
affected, but an estimated 99% of the mortality was 
in the grebe population. The outbreak was 

Pickup of dead snow geese during an avian cholera die-off 
in South Dakota. The bacteria (Pasteurella multocida) 
responsible for this disease survive for many weeks in the 
carcasses of dead birds. Scavenging by other birds, such 
as raptors, exposes them to the disease and further 
contaminates the areas where the carcasses lie, thereby 
increasing the exposure of waterfowl and other birds using 
the areas to the disease. Photo by M. Friend 

Burning snow geese during an avian cholera die-off in 
South Dakota. Carcass weight of over 3 tons was disposed 
of by this means during the epizootic. Burning is the best 
way of destroying this contaminated material; rubber tires 
and diesel fuel were the principal fuels used. Photo by M. 

evidently acute, since no sick birds were seen before 
the storm, and the dead dotted the shoreline when 
the snow melted on November 29. 

Erysipelas, best known in swine and turkeys, is 
caused by a bacterium, Erysipelothrix rhusioputhiae. 
It is transmissible to man, causing an infection, 
usually localized, called erysipeloid (unrelated to 
human erysipelas). The disease has been found in 
many species of wild birds and mammals, but 
mortality of comparable severity has never been 

Because of the potential health hazard to man 
and other vertebrate species, one or two bird 
carcasses were examined each week after the 
diagnosis was confirmed to ascertain how long E. 


rhusiopathiae would remain viable in decomposing 
grebe tissues. The last isolation was made on June 3 
— more than 6 months after the outbreak. Of 
possible epizootiological significance was the 
isolation of the bacterium from blowfly maggots 
from a decomposing grebe carcass. 

Bacteriophages and Production of Botulinum 
Toxin. — In 1970, workers in Japan first reported 
that the capacity of at least some types and strains 
of Clostridium botulinum to produce toxin is 
dependent upon their being infected with specific 
viruses (bacteriophages). If the bacteria are relieved 
of their bacteriophages by treatment with chemicals 
or exposure to ultraviolet light, they remain 
biologically the same except that they no longer 
produce toxin. 

C. botulinum is a hardy, spore-forming 
bacterium. Any treatment of a marsh drastic 
enough to destroy C. botulinum would probably 
also destroy the essential microorganisms and 
invertebrate life of the marsh. Studies are under 
way to determine the feasibility of attacking the 
bacterium by way of its bacteriophages on the 
assumption that they would be more susceptible to 
adverse chemical and physical agents. 

The bacteriophages for study were separated 
from the bacterial cells by passing cultures through 
filter membranes that retain bacteria but permit 
passage of viruses. 

Briefly summarized, the findings were: (1) 
Bacteriophages from a toxigenic strain of C. 
Botulinum did in some cases reinfect the same 
atoxigenic strain cured of its infection and thereby 
restored its toxigenicity; all atoxigenic strains could 
not be reinfected. (2) Bacteriophages from one 
type-C strain did not necessarily reinfect atoxigenic 
cells of another strain. (3) Survival of bacteriophages 
was not affected by salinity (sodium chloride) in 
concentrations in the range of 0.1875 to 3%; in 
concentrations of 6, 12, and 24% they survived for 5 
hours, but not for 24 hours. (4) Bacteriophages died 
in less than 1 hour at pH 4.0; from pH 5.0 to 8.0, 
they survived for at least 24 hours; and at pH 9.0 
they were alive at 4 hours but not at 24 hours. 

Lesser Scaups Killed by Coccidiosis During 
Spring Migration. — A die-off of 250 lesser scaups 
on the Bluestream Reservoir near Lincoln, 
Nebraska, during March 1976 was due to massive 
intestinal coccidial infections by Eimeria aythyae. 
This is only the third known die-off due to this 
parasite. All have occurred in lesser scaups, during 
spring migration, and in the Midwest. The parasite 
has not been found in any other host. 

Immunity to Botulism in Ducks Strengthened by 
Oral Administration of Toxin. — Studies reported 
earlier showed that groups of mallard ducks given 
repeated sublethal doses of Clostridium botulinum 
type-C toxin by the oral route were no more 
refractory to experimentally induced botulism than 
were untreated control groups, whereas similar 
birds given the same doses of toxin by the 
intramuscular route became solidly immune. 

According to studies completed in 1975, 
however, some mallards with a basic immunity 
conferred by injections of toxoid (followed by 
active toxin) showed a marked serum antibody 
response to orally administered toxin if the dose 
was large enough. Others, even though their 
antibody levels increased only slightly, if at all, after 
oral challenge, appeared to be as resistant to 
intoxication as were those with high antibody titers. 
A few birds did not respond immunologically, 
showing no antibody increase and not enough 
protection to prevent death after three or more 
challenges. A possible reason an attack of botulism 
confers no immunity on wild birds is that a dose of 
toxin large enough to stimulate production of 
antibodies would ordinarily be lethal. 

Large-scale immunization of wild birds is 
impracticable; but enough data are available to 
indicate that rare and endangered species, for 
example, subject to risk of botulism, once 
immunized by the injection of toxoid, may 
maintain their immunity by naturally acquired oral 
doses of toxin. 

Captive Cranes Afflicted by Several Parasites 
and Bacterial Diseases. — Wildlife reared in 
captivity is subject to diseases that may nullify the 
intent of a rearing program. This is especially true 
when progeny of captive stock are to be released to 
supplement existing wild populations or to 
establish new breeding populations. Parasites and 
diseases acquired in captivity may also be released 
along with the wildlife, and therefore it is important 
to monitor the health of captive wildlife prior to 

In one survey a collection of 92 cranes, 
representing 14 species, were tested. A blood 
protozoan parasite of the genus Haemoproteus was 
identified in an East African crowned crane and a 
hooded crane. Salmonella typhimurium was 
isolated from two East African crowned cranes and 
a Japanese crane, and Salmonella kentucky was 
isolated from a wattled crane. Of 79 fecal samples 
examined from these cranes, 32 contained the 
coccidian parasite Eimeria reichenowi, 36 had 


Avioserpentiasis in a western grebe. The swelling above 
the superior mandible and the one below the inferior 
mandible result from the invasion of the connective tissue 
by female nematodes of the genus Avioserpens. Photo by 
J. T. Ratti. 

Eimeria gruis, 2 had Capillaha spp., 1 had eggs of 
another nematode, and 1 had fluke eggs. All tests 
for Newcastle Disease Virus and Influenza Virus 
were negative. 

Since the survey, an East African crowned crane 
and a sarus crane have succumbed to a bacterial 
disease caused by Erysipelothrix spp. A Japanese 
crane severely affected with gapeworn {Cyathostoma 
spp.) was successfully treated with thiobendazol. 

Nematode Infection in Western Grebes. — In 
July 1975, a western grebe with tumorlike swellings 
posterior to both the upper and lower mandibles 
and encircling both hock joints was submitted to 
the Bear River Research Station for diagnosis. 

Microscopic examination of these turgid tissues 
disclosed that they were teeming with the mature 
and larval forms of the nematode Avioserpens sp. 
Two more grebes, with swellings posterior to the 
lower mandible only, were examined later in the 
summer, and milder infections with the same 
organism were observed. 

This parasite has been reported in several species 
of birds, but never before in the western grebe. It 
may sometimes cause death by asphyxiation; in 
other cases the tumor is slowly resorbed and 
replaced by fibrous tissue. 


Electrocution is a common cause of mortality among bald 
and golden eagles. The ruptured vesicules at the base of 
this golden eagle's talons are the result of electrocution 
from a high-tension line. Photo by E. A. Bell 

Undescribed coccidian parasite from the intestine of a 
bald eagle. This parasite probably belongs to the genus 
Isospora and has been observed in several bald eagles 
necropsied at the National Fish and Wildlife Health 
Laboratory. Photo by E. A. Bell 

Status of Seabird Populations in the Gulf of 
Alaska. — A survey of nesting seabirds on 
Middleton Island in the Gulf of Alaska was 

conducted for the second consecutive year. Sample 
plots were established for comparisons of breeding 
productivity in future years. Black-legged kittiwakes, 


in contrast to most other colonial species around 
Alaska in 1976, experienced good breeding success; 
eggs were found at over 50% of the occupied sites. 
Production of young was estimated to be 
approximately one per active nest — nearly 23,000 
for the entire colony. Pelagic cormorants also 
appeared to be successful, with nearly 1.7 eggs or 
young per nest halfway through the breeding 
season. A previously unknown colony of about 800 
pairs of rhinoceros auklets was discovered in 1976. 

An investigation of nest-site selection by 
kittiwakes revealed that although steeper cliff faces 
support the largest populations, more gradual 
slopes are preferred for nest placement within any 
given segment of cliff. Data are being analyzed for 
correlations of nesting phenology and productivity 
with the angle and height of the slopes on which 
nests are placed. 

Status of Birds of the New York Bight. — A 
comprehensive report on the historical and present 
status of marine and coastal birds of Long Island 
and New Jersey was prepared for publication in the 
Atlas Monograph series of the Marine Ecosystems 
Analysis (MESA) Program. The manuscript 
discusses the status of important avian components 
of the Bight, with emphasis on population changes 
during the 20th century and the reasons for these 
changes. Other chapters deal with the effects of 
environmental contaminants on birds of the Bight, 
the problem of birds and aircraft, effects of habitat 
disturbance on bird populations, effects of hunting, 
birds as vectors of disease, and recreational benefits 
of birds. It was concluded that habitat modification 
and excessive hunting for commercial purposes 
have had the most significant detrimental effects on 
birds of the Bight but that the increasing 
background levels of environmental contaminants 
such as pesticides and oil are potentially serious 

Biology of Royal Terns. — The royal tern 
provides an example of a species that is potentially 
vulnerable to a variety of human influences. These 
birds nest in a relatively few large colonies on sandy 
barrier islands along the Atlantic and Gulf coasts. 
They are therefore susceptible to disruption by 
coastal land development, recreational use of 
beaches, and oil spills. Because the normal clutch 
consists of only one egg, reproductive potential is 

Royal terns are normally 3 years old when they 
nest for the first time. Their age at first breeding is 
thus the same as that of several species of smaller 
terns, such as the common tern, and less than that 
of various gulls that are more similar to the royal 

tern in size. Some royal terns return to breed at the 
same colony sites where they were hatched or where 
they nested in previous years; others nest in 
different colonies. In addition, locations of major 
colonies may shift from year to year. This ability to 
establish colonies in new locations is obviously a 
favorable adaptation in a changing environment. 
The way in which human activities can both 
harm and benefit wildlife is well illustrated by this 
species. Some traditional nesting sites are no longer 
suitable because of heavy recreational use of 
beaches by swimmers, picnickers, and beach-buggy 
fans. On the other hand, channel dredging in 
adjacent shallow ocean inlets has created sandy 
islands that are free of mammalian predators and 
often relatively free of human disturbance. These 
islands are accepted by the birds and often provide 
better nesting habitat than natural beaches. Once 
grass and shrubs take hold, these spoil islands 
become unsuitable for terns but are attractive to 
nesting gulls and wading birds. Dredging of 
channels can be potentially useful as an intentional 
rather than a fortuitous means of creating habitat 
for royal terns and other colonial aquatic birds. 


Duck Nesting and Vegetation Quality. — An 

understanding of the nesting habitat requirements 
of certain duck species and other ground-nesting 
birds has been gained from measurements of 
vegetation in fields and at nest sites. 

Visual obstruction readings were taken at 100 
plots along linear transects in 7 quarter-section 
fields during the last half of May. These fields were 
searched for nests three times during the nesting 
season. Visual obstruction readings were taken at 
all nests located. The data from fields where 
vegetation was similar in height and density were 
lumped. Four fields totaling 496 acres had mean 
visual obstruction readings ranging from 0.6 to 0.8 
dm, two fields of 249 acres had mean readings of 1 . 5 
to 1.6 dm, and one field of 104 acres had a mean of 
3.2 dm. Mallards, gadwalls, pintails, blue-winged 
teals, and northern shovelers all demonstrated 
apparent preference for fields with the tallest, most 
dense vegetation. Twenty-three dabbling duck 
nests per 100 acres were found in the cover with 
mean 100% visual obstruction of 0.6 to 0.8 dm, 39 
nests per 100 acres in the 1.5- to 1.6-dm cover, and 
63 per 100 acres in the 3.2-dm cover. An interesting 
finding is that upland sandpiper nests were not 


found in the 3.2-dm cover and were most plentiful 

in the 1.5- to 1.6-dm cover, whereas American 

bitterns and deer fawns were found only in the 

3.2-dm cover. 
The range of 100% visual obstruction readings at 

nest sites of various species is important. Mallard 

nests were found at sites with mean readings of 1.25 

to 6.25 dm (average 3.79); gadwall nests, 2.00 to 

4.37 dm (average, 3.61); nests of pintails, 2. 12 to 

5.12 dm (average, 3.29); blue-winged teals, 0.25 to 

6.25 dm (average, 2.04); northern shovelers, 1.62 to 

3.20 dm (average 2.14); upland sandpipers, 0.25 to 

2.00 dm (average, 1.09); and American bitterns, 

4.12 to 8.75 dm (average, 6.05). It is obvious that 

habitat managed for various species of ducks will 

benefit a variety of other wildlife species. 

Response of Nesting Ducks to Seeded Cover. — 
The main objective of studies of duck nesting in 
fields of undisturbed grass-legume cover, conducted 
since 1968, was to obtain information on which to 
base management of upland nesting cover in the 
prairie pothole region. Studies on nine 30- to 130- 
acre fields of undisturbed smooth bromegrass- 
alfalfa cover in Edmunds County, South Dakota, 
during 1971, 1972, and 1973 indicated that this 
habitat type was productive of ducks. During the 3 
years, 620 duck nests were studied: 38% blue- 
winged teal; 24% mallard; 24% gadwall. The 
average density was 31 nests per 100 acres, and the 
average rate of hatch was 56%. 

Various mixtures of introduced cool-season 
grasses and legumes have been planted on cropland 
fields at the Center's Woodworth Station to test 
their value as nesting cover for ducks. Principal 
species of vegetation used for the planting trials 
were intermediate wheatgrass, tall wheatgrass, 
alfalfa, and sweet clover. On a per acre basis, 
production of ducks from planted cover 3 to 5 years 
old has generally been higher than that from other 
nesting habitats on the study area. An 82-acre 
cropland field planted to cover in 1972 proved to be 
a good nesting area in 1975. The cover mixture 
planted on the field was 5 pounds of intermediate 
wheatgrass, 3 pounds of tall wheatgrass, 2 pounds 
of alfalfa, and 2 pounds of yellow sweet clover per 
acre. By 1975, the fourth growing season after 
planting, the vegetation had developed into an 
excellent stand. 

Three complete nest searches during the 1975 
nesting season revealed 56 duck nests, 9 American 
bittern nests, 1 marsh hawk nest, and 1 ring-necked 
pheasant nest on the 82-acre plot. Hatch success of 
the duck nests was 48%. A variety of passerine birds 
also used the cover for nesting. Short-billed marsh 

Mallard clutches are well protected from climatic extremes 
by the surrounding vegetation and the thick blanket of 
down and grass that the hens place around the eggs. 
Photo by J. T. Lokemoen. 

A hatched mallard nest showing the diagnostic way the 
membranes and eggshell appear when theducklings leave 
the egg. Photo by J. T. Lokemoen. 


Although the upland sandpiper is a shorebird, it is seldom 
found near ponds but inhabits the prairie uplands and 
often perches on raised objects such as this fence post. 
Photo by J. T. Lokemoen. 

Redhead ducks often lay eggs in nests of other waterfowl 
species. This picture shows a light-colored redhead 
duckling (foreground) that was hatched in a lesser scaup 
nest. Photo by J. T. Lokemoen. 

wrens and common yellowthroats were very 
abundant. Other species that nested in lesser 
numbers were Savannah sparrows, red-winged 
blackbirds, and western meadowlarks. Use of the 
plot by nesting birds in 1975 represents a dramatic 
increase from the time it was idled from farming 
and planted with a grass-legume cover. In 1971, 
when the land was farmed, only one duck nest was 
found. The number then increased to 7 in 1972, 18 
in 1973, and 25 in 1974. 

Prairie Mallards Nest in Marshes. — Nest data 
gathered during the 1974-76 field seasons indicate 
that mallards regularly nest overwater in Class IV 
wetlands. This information is based upon nesting 
attempts made by radio-tagged and by unmarked 
hens on upland and wetland habitats of the study 
area. Seven of 14 nests initiated by seven radio- 
marked hens in 1974 and 1975 were in wetland 
habitat. Sixty-seven percent of the 46 active 
mallard nests located during the 1976 field season 
were overwater in 15 wetlands. Mallards generally 
selected nest sites in shallow water amid rank stands 
of old-growth cattails or hardstem bulrushes, or 
both. Other wetland habitats, although plentiful on 
the study area, were not used for nesting but were 
important in other aspects of their nesting and 
brood-rearing ecology. Overwater nest distribution 
on the study area reflects spacing of ponds 
supporting dense stands of cattails or bulrushes, or 
both. The highest density of nests overwater in 
emergent vegetation was seven on a 10.9-acre pond. 

Mallard use of wetland habitat for nesting on a 

regular basis is significant from both research and 
management viewpoints. The structure and form of 
overwater nests indicate considerable adaptation 
for nesting in wetland habitat, which suggests a 
long-standing association with it. Whether 
individual ducks readily shift between upland and 
wetland nesting habitats is not known. The limited 
data available lend some support to the hypothesis 
that relatively discrete subpopulations of upland 
and wetland nesters may exist in the region. 
Because of adverse pressures being exerted in 
upland habitats, the relative contribution by 
overwater nesters to annual production in the 
prairie pothole region may have risen markedly in 
recent years. In retrospect, the immediate and 
widespread use of nest baskets by mallard hens, 
when first introduced into North Dakota marshes a 
decade ago, presumably occurred because a sizable 
segment of the population was already adapted to 
nesting overwater and was seeking nest sites there. 
Baskets provide an acceptable alternative to 
natural vegetation for some of the overwater 
nesters, and high rates of reproductive success in 
these structures result in high homing rates, as 
documented in previous studies. 

Foods of Prairie-dwelling Raccoons. — Few 
definitive studies on the raccoon have been 
conducted in the prairie pothole region, an area in 
which they have only recently become well 
established. This study was initiated to identify the 
feeding strategies of prairie-dwelling raccoons, 
including their relationship to nesting waterfowl in 


the principal waterfowl production region of North 

Radiotelemetry was used to study the nocturnal 
activities of a sample of individual raccoons 
throughout the avian nesting season. Detailed data 
relating animal activity to habitat type throughout 
specified time periods were accumulated. Simultaneous 
collection and analysis of raccoon fecal material 
yielded information on foods eaten. 

In 1974, bird remains occurred in 27, 35, 37, and 
17% of the raccoon fecal passages examined in 
April, May, June, and July, respectively. Field 
observations of telemetered raccoons indicated that 
a large percentage of the avian material was from 
carrion. In the same 4 months of 1975, avian eggs or 
embryos, or both, were found in 8, 26, 59, and 42% 
of the fecal passages examined. Also found 
consumed in increasingly greater frequencies 
throughout those 4 months were mollusks (3, 18, 
53, and 58%, respectively) and insects (30, 35, 58, 
and 58%, respectively). Grain, a staple item, was 
found throughout the summer in 67 to 95% of the 
fecal passages examined during both years. 

This study indicated that the raccoon most 
probably has a significant impact on the nesting 
success of some avian species in the prairie pothole 
region, though it appears less important as a 
predator on adult nesting birds. Waterfowl and 
other water birds are strongly indicated as the 
principal bird species affected. 

Prairie Raccoons: Mobility and Habitat Use. — 
Raccoons have been considered one of the principal 
predators of duck nests in the prairie pothole 
region. In 1973, a 3-year study was initiated to 
determine movement and habitat use patterns of 
prairie raccoons and to relate them to potential 
depredations on waterfowl nests. Radiotelemetry 
was used to monitor raccoon activities during the 
waterfowl breeding season (April-July) on an 
intensively farmed region in eastern North Dakota. 
The 48-square-mile study area contained numerous 
large marshes, including several Waterfowl 
Production Areas. 

Most individuals in the sparse (approximately 
two per square mile) raccoon population were 
equipped with radio transmitters. Movement 
patterns and home ranges varied with the sex, age, 
and reproductive status of the individual raccoon. 
Adult males moved regularly throughout home 
ranges that averaged 9.9 square miles, often 
covering the entire area in 2 or 3 nights. 
Relationships between individual raccoons and the 
absence of significant home range overlap 
suggested a form of territoriality among adult 

males. A distinct dispersal characterized the 
movements of nonbreeding yearling males in May, 
June, and July. Unidirectional movements of 5 
miles in 1 night were not uncommon during 
dispersal. Mean seasonal home ranges of yearling 
males averaged 4.4 square miles; home ranges 
before and after dispersal were similar in size. 
Parous or pregnant females, including six adults 
and one yearling, had home ranges averaging 3. 1 
square miles. Movements were confined to smaller 
(often less than 100 acres) home ranges around the 
litter site for 4-5 weeks after parturition. 
Nulliparous yearling females did not disperse and 
had home ranges averaging 2.5 square miles. 

Although 82% of the nocturnal locations and 
94% of the diurnal locations of the raccoons were in 
building sites, wooded areas, and wetlands, those 
three habitats made up only 10% of the study area. 
Use of wetlands increased concomitantly with 
decreased use of building sites throughout the 
April-July study period. Upland habitats such as 
pastures, hayfields, and dense, idle cover were 
seldom used by raccoons. 

The varying movement patterns among the 
different sex-age groups suggest that the potential 
for nest depredation is also variable among groups. 
Nevertheless, the extremely large, well-patrolled 
ranges and the definitive patterns of habitat use of 
prairie raccoons suggest that a relatively small 
population has the potential for destroying many 
nests in widely separated islands of nesting cover. 

Renesting Capabilities of Blue-winged Teal. — A 
study of the impact of changing limnological 
conditions on the renesting capabilities of known- 
age blue-winged teal was undertaken on 0.1 -acre 
experimental ponds in light of four known factors: 
(1) Studies of the feeding ecology of breeding 
dabbling ducks on the North Dakota prairies have 
demonstrated that aquatic invertebrates dominate 
the diet of laying hens; (2) aquatic invertebrate 
populations inhabiting prairie wetlands are subject 
to extreme fluctuations in response to changing 
limnological conditions; (3) the impact of aquatic 
habitat on initial and renesting attempts of 
waterfowl is unknown; (4) aquatic invertebrates 
respond readily to habitat manipulation. 

Yearling blue-winged teal females with easy 
access to an abundant invertebrate population were 
capable of producing four clutches of eggs. Two- 
year-old females that had fewer food resources 
subsequently reduced egg production below their 
level of performance as yearlings. Three-year-old 
blue-winged teal females were capable of producing 
five clutches of eggs when supplied a high protein 


3*52 * 

}ies*m J 

Although this blue-winged teal brood appeared to be feeding on duckweed, they were actually taking small snails, a 
favored food item. Photo by J. T. Lokemoen. 

supplemental diet or a dense population of 
invertebrates. One hen laid 53 eggs, the weight of 
which exceeded her spring body weight by 3.8 
times. Productivity, hatch success, and duckling 
survival up to 7 days of age were determined for 
hens held on different food regimes. 

Tenth-acre experimental ponds were manipulated 
to produce an abundant invertebrate population 
capable of supporting a pair of blue-winged teal 
with sufficient protein to enable them to produce 
the maximum number of eggs. The same ponds, 
when manipulated to produce a minimal food 
supply, were incapable of providing sufficient food 
to maintain a pair of blue-winged teal. 

Control birds fed a supplemental high protein 
diet increased their egg production from yearlings 
to 3-year-olds. Although egg production increased 
with time, laying characteristics associated with 
individual birds persisted. Females that were the 
most productive as 1 -year-olds were also the most 
productive as 3-year-olds. 

An assessment of ovary development in 77 wild 
birds examined from the immediate area, and the 
initiation of late clutches and broods found in the 

wild, suggest that the phenology of nest initiations 
in pen studies is similar to that found in wild birds 
during years of abundant precipitation. 

Postbreeding Activities of Mallards and Wood 
Ducks in North-central Minnesota. — Telemetry 
techniques were used to monitor the postbreeding 
activities of 129 mallards and 1 18 wood ducks on a 
932-km 2 area of north-central Minnesota. Upon 
completion of breeding activities and before the 
flightless period, all mallard drakes departed the 
area; this exodus peaked during early June. Nesting 
success may have influenced the departure of 
postbreeding mallard hens. Of the broodless hens, 
35% remained on the area, whereas half of the hens 
raising broods spent the flightless period on their 
breeding areas. An estimated 39% of the mallard 
hens on the area in the spring were present at the 
beginning of their flightless period. Tracking data 
and band recoveries indicated that most hens that 
moved out of the area probably remained within a 
160-km radius and that some returned to the study 
area either before or during the fall migration. 
About 50% of the drake wood ducks and 40% of the 
hens left the breeding area before wing molt. The 


timing of wood duck departures was similar to that 
of mallards. The flightless period of mallards and 
wood ducks began in mid-June for wood duck 
drakes and lasted into early October for some 
mallard hens. Late-molting mallard and wood duck 
hens all reared broods that same year. A minimum 
of 29% of the mallard hens on the study area in 
spring were still there at the beginning of the 
hunting season in early October. About 14% of the 
wood duck males and 43% of the females breeding 
locally remained on the area until early October. 
About 22% of the mallards and 16% of the wood 
ducks that reared broods were killed on the study 
area, compared with 9% of the broodless mallards 
and 5% of the broodless wood duck hens. Principal 
habitats used by postbreeding mallards were bays 
of large lakes with abundant emergent cover, 
particularly wild rice. Wood ducks tended to use 
similar habitat but also frequented small woodland 
ponds and flowages, especially after the flightless 


Residential Development Affects Adjacent 
Urban "Natural Area." — In northern Baltimore, a 
very dense development — Cold Spring Town — is 

being constructed immediately adjacent to an old, 
established natural area, Cylburn Park, providing 
the opportunity for a case history study. Systematic 
bird counts were made in four areas: in Cylburn 
Park, in a proposed buffer area between the Park 
and Cold Spring Town, in the area to be covered by 
Cold Spring Town, and in an old residential area 
adjacent to the new development. These data 
provide base-line information on the characteristics 
of the bird populations in the area before the 
development of Cold Spring Town is completed. 
They also provide information on the characteristics 
of bird populations associated with various 
habitats. For example, the densest breeding bird 
population occurred in the old residential area 
located just west of the Cold Spring Town 
construction site; the lowest density occurred in 
Cylburn Park, the established natural area. The 
residential area is a stable, middle-income 
community consisting primarily of detached homes 
at a density of about 10 dwelling units per acre. 
Over half the birds in this area were house 
sparrows, starlings, and pigeons, but the "native" 
bird population of mockingbirds, catbirds, robins, 
cardinals, and song sparrows was nevertheless 
higher than in undeveloped areas. The mature 
woods in Cylburn Park had the lowest density of 
birds but a good variety of species was present. 

Mammals and Nonmigratory Birds 


Abandoned Eastern Strip Mines Support Wildlife. 

— Most surface coal mines worked before the 
passage of reclamation laws in the mid-1960's have 
developed productive wildlife habitat through 
natural succession. A cooperative study by 
personnel of the Denver Wildlife Research Center, 
the Virginia Cooperative Wildlife and Fishery 
Research Units, and Virginia Polytechnic Institute 
and State University has been undertaken to define 
the beneficial and adverse impacts on wildlife 
habitat for Virginia's 18,000 acres of abandoned 
mine lands and to determine the amount of 

reclamation that is justified. Evaluation of wildlife 
use of 5-acre segments of 12 mined areas was 
completed, showing that approximately the same 
number of species of small mammals was found on 
4 poorly vegetated, 4 medium vegetated, and 4 well- 
vegetated plots; however, the number of small 
mammals captured in 3 nights of kill trapping was 
related to the amount of vegetation, with 57, 81, 
and 99 being caught in the three types of habitat, 

In contrast, a greater variety of songbirds was 
found in habitats with poor and medium vegetation 
than in well-vegetated habitat. Totals of 37, 40, and 
32 species were found on three types of habitat 


sampled. A detailed analysis of factors associated 
with the amount of vegetation indicated that soil 
potassium was most important. Failure to develop 
any vegetation at all was best explained by low pH. 
Nitrogen was not measured. Information gained 
from this study promises to be useful in an extensive 
reclamation project now under way in Virginia, 
Tennessee, Kentucky, and Alabama. 

Golden Eagle Populations in the Western States. 
— This study, designed to monitor changes in the 
population status of golden eagles, was started in 
Texas and New Mexico in 1964. In 1971 it was 
expanded to include important wintering areas in 
Colorado, Idaho, Utah, and Wyoming; in 1972, 
Montana was added; and in 1973, similar areas in 
Arizona, Nevada, Oregon, North Dakota, and 
South Dakota were included. 

The cottontail rabbit is an important prey species for 
eagles and other raptors on the Montana-Wyoming coal- 
lease areas. Photo by D. E. Biggins. 

During the wintering period of January- 
February 1976, flights over randomly located 
transects through study areas totaling 62,100 
square miles in eight western States showed an 
average density of 1 1 .0 golden eagles per 1 00 square 
miles (Arizona, Oregon, South Dakota, and Texas 
were not covered this year). Results of flights 
conducted over the same areas in 1973, 1974, and 
1975 showed densities of 15.5, 12.2, and 10.5, 
respectively. Ranked in descending order, the 

largest populations, as in previous years, were 
found in Wyoming, northwestern Colorado, and 
west-central Utah; lowest wintering numbers were 
in North Dakota. The greatest yearly fluctuations 
in eagle numbers occurred in northwestern 
Colorado, Idaho, Nevada, and Utah; populations 
in Montana and Wyoming remained relatively 
constant. The decline between 1973 and 1975 
closely paralleled decreased nesting activity and 
productivity noted for golden eagles during the 
same years in companion nesting studies. A 
population "crash" of both jackrabbits and 
cottontails, the mainstays of the golden eagle's diet 
throughout much of the intermountain region 
during this period, is believed responsible. Future 
changes in golden eagle populations in winter will 
be monitored at 3-year intervals by flights over 
study areas. 

Report on the Status of Peregrine Falcons in 
Baja California. — The peregrine falcon has 
declined drastically throughout much of North 
America during the past several decades. Although 
the decline is attributed largely to the use of 
organochlorine pesticides (especially DDT), 
habitat destruction, shooting, disease, and other 
factors were also implicated. 

Knowledge of the status of the peregrine in Baja 
California and other parts of Mexico is important 
because these southern populations could become a 
natural reservoir for repopulation by dispersion 
into the United States. Baja birds could also be a 
source of captive breeding stock for reintroduction 
into the United States. Peregrines have been 
reported to nest in good numbers in Baja, with over 
50 known eyrie sites. 

In 1976, a preliminary survey revealed a nearly 
complete absence of activity at 16 historic eyries 
along the Pacific Coast and in inland areas of the 
peninsula. Although time did not permit checking 
of 13 historic sites on Pacific islands, only 1 site is 
reported to have supported peregrines in recent 
years. Peregrines were sighted on 9 of 23 islands 
surveyed in the Gulf of California, and other 
observations reported them on 3 additional islands. 

During the survey 27 peregrines were sighted — 
paired birds at 10 sites and 7 unpaired birds. Two 
active eyries were located. Two eggs were found at 
one eyrie site, and two newly fledged young and one 
addled egg were found at the other site. Food 
remains at the two eyries indicated that peregrines 
nesting in the Gulf of California prey upon a wide 
variety of avian species, including gulls, grebes, 
terns, murrelets, and warblers. Additional data on 
the status, food habits, eyrie characteristics, 


pesticide residues in eggs, and prey species are 
needed for Baja California and interior Mexico. 

Interior Least Terns Surveyed. — Least terns 
throughout the world are encountering difficulty 
due to changing or disappearing habitats, 
disturbance by humans, and other factors. Such 
problems have been well documented in recent 
years for our California least tern (now considered 
to be endangered) and the eastern subspecies, but 
no formal study has been made to determine the 
status of the subspecies that inhabits the Mississippi 
River and Great Plains. A low-level aerial survey of 
2,000 miles of rivers during June 1975 showed that 
only 1,250 least terns nest in the vast area from New 
Mexico to Nebraska to Tennessee. Best estimates 
for each river system surveyed are as follows: Pecos, 
50 birds; Brazos, none; Red, 25; Canadian, 25; 
Cimarron, 100; Arkansas, 50; Republican, none; 
Platte, 150; Niobrara, 150; Missouri, 100; 
Mississippi, 600; and Ohio, none. The construction 
of reservoirs and farm ponds in recent decades has 
reduced the frequency and severity of flooding, 
allowing the bare sandbars needed for nesting to 
become vegetated. Massive salt sources in portions 
of the Arkansas, Cimarron, Canadian, Red, 
Brazos, Colorado (Texas), and Pecos rivers largely 
prevent the water from being used for municipal, 
industrial, or irrigation purposes. Planned control 
measures will affect least terns directly by flooding 
four of the salt flats where they nest and indirectly 
by making the water so useful to humans that little 
will be left to support the small fish that the terns 
need for food. Additional improvements in 
navigation channels, planned for the Missouri and 
Mississippi rivers, may prevent the formation of 
enough sandbars. Periodic surveys are recommended 
to monitor changes in populations of least terns. 

National Elk Refuge Research. — The objective 
of the National Elk Refuge located at Jackson, 
Wyoming, is to manage the area as elk winter range. 
This management program means that all forage 
grown on the refuge is left standing for the elk to 
take on a "free-ranging" basis. Better distribution 
of the elk over the available winter range will insure 
better utilization of the natural forage and reduce 
the need for supplemental feeding. 

In the past, supplemental feed was in the form of 
baled hay. Research initiated in 1970 identified 
pelletized alfalfa as a good supplemental feed, and 
for the past two winters all of the elk (in excess of 
7,500) have been fed alfalfa pellets during a portion 
of the winter (usually from mid-February through 
March). One man, using a 20-ton-capacity six- 
wheel-drive truck, has been able to feed 7,500 elk in 

less than 5 hours each day. When baled hay was 
used, six men, working 8 hours per day, were 

Current research has included studies to 
determine the minimum daily ration of alfalfa 
pellets. Baled hay was fed at the rate of 10 pounds of 
hay per elk per day. Alfalfa pellets have been fed at 
the rate of 8 pounds per elk per day. Research 
conducted during the winter of 1976 indicated that 
possibly 5 pounds per animal per day or less can be 
fed without detrimental effects on the elk or their 
reproductive success. The approximate 38% 
reduction in the amount of money spent for 
supplemental feed would be a significant saving. 

Kenai Moose Research Center. — The Denver 
Wildlife Research Center, Kenai National Moose 
Range, and Alaska Department of Fish and Game 
are participating in a unique moose research project 
in the northern Kenai Lowlands of the Moose 
Range. Biologists from the Alaska Department of 
Fish and Game, who are responsible for moose 
biology research, are actively involved in studies of 
moose physiology, movements, and population 
dynamics. The U.S. Fish and Wildlife Service, 
responsible for moose habitat research, is 
investigating browse quality, production, and use 
in four 1 -square-mile enclosures that make up the 
Kenai Moose Research Center. 

In the Kenai area, paper birch is the most 
abundant browse plant and makes up the greatest 
proportion of forage in moose diets. The table 
below shows moose densities per square mile and 
percentage of birch plants browsed in the four 
enclosures and in outside stands over the 3-year 
period 1973-75. The percentage of plants browsed 
follows fairly closely the average overwinter 
densities of moose in each enclosure. 

1973 1974 


Moose Moose 


Pen population Browsed population 




(per mi 2 ) birch (%) (per mi 2 ) 

birch (%) 

(per mi 2 ) 

birch (%) 

1 11 




2 14 35.8 14 




3 7 35.6 9 




4 28 58.1 19 







At first glance, it appears that up to 15 or so 
moose per square mile on a 7-month basis is not too 
high a density with respect to percentage of birch 
plants browsed, but two factors influence the 
overall effect on the supply of birch. One factor is 
the high snowshoe hare populations, so that the 
percentage of plants browsed by moose and by 
hares is considerably higher than that shown in the 


I ' 

Moose on the Kenai Peninsula have entered a period of 
decline as a result of successional changes in moose 
habitat, severe winters, hunting, and losses to predators. 
Current research is designed to determine wolf density, 
predation patterns, and the effects of predation on moose 
populations. Photo by R. O. Peterson. 

table. The second is that 40% of the birch plants are 
under 1 m tall and only 20% of the birches eaten by 
moose are in that category. Therefore, the 
percentage of birches over 1 m tall that are browsed 
by moose is greater than what is shown in the table. 
A close examination of the response in annual 
production of birch to browsing will be required to 
understand fully the influence on birch populations 
at these various levels of use. 

Though the moose populations in the enclosures 
appear to be extremely high, populations adjacent 
to the Moose Research Center are also high during 
the winter. This adjacent area is part of the 1947 
burn and is known to support large moose 
populations. Winter censuses have documented 8 
to 37 moose per square mile in the area, which 
probably explains the high use of birch stands 
outside the Center. 

Browse Manipulation on Kenai National Moose 
Range. — In 1974, the Denver Wildlife Research 
Center and the Kenai National Moose Range 
initiated a research program to study the effects of 
prescribed burning and of crushing trees and shrubs 
by LeTourneau Tree Crushers on a 27-year-old 
burn on the Moose Range. Three areas were 
selected for the study; crushing of woody growth 
was scheduled for one, vegetation on another was 
to be burned, and an adjacent area was the control. 
During the winter of 1974-75, woody plants on 
about 1,500 acres were crushed. The prescribed 
burn has not yet occurred because of unsatisfactory 
weather or fuel conditions. Where about 35% of the 

forest was not burned in 1947 and remains as 
islands of cover surrounded by stands of spruce and 
paper birch regrowth, paper birch is the dominant 
forage species for moose. Willow and aspen are 
consistently overbrowsed so that they are in 
decadent condition and produce little annual 
growth. From the present study we hope to 
determine which method of disturbance results in 
the fastest production of browse and which habitat 
types respond best to planned disturbance. 

Crushing was effective from two standpoints. 
Density of competing spruce saplings was reduced 
in the regrowth stands by 68-81%. This reduction 
frees light, water, and nutrients for browse species 
and may be the most important effect of the 
crushing. Browse density has increased. In what 
used to be mature stands of spruce, aspen, or birch, 
density of aspen has increased in some cases from 
0.3 plant per 5 m 2 before crushing to 7.7 plants per 
5 m 2 after crushing. Birch has responded almost as 
well, and willow is now growing in some of those 
stands where it was absent before. In what used to 
be regrowth stands, the changes have not been as 
dramatic. Birch is now reaching precrushing 
densities of 2-10 plants per 5 m 2 , and aspen and 
willow in some stands are denser now than prior to 

Although increased density is a desired result of 
both disturbance techniques, we also hope to 
obtain a good mixture of the three browse species 

Moose calf survival on the Kenai National Moose Range 
has been low in recent years. Causes of early mortality of 
calves and the influence of predation on calf survival are 
under investigation. Photo by R. O. Peterson. 


Average number of selected bird species on three study plots of an Apache- Sitgr eaves National Forest 
study area (1973-74 pretreatment, 1975-76 posttreatment). 


(snag removal) 


[snag retention) 

C (control) 

Bird species 



















+ 13 




Gray-headed junco 



+ 147 






+ 155 

Mountain chickadee 










Pigmy nuthatch 
















+ 164 



+ 17 

Steller's jay 










Violet-green swallow 










Warbling vireo 










White-breasted nuthatch 










Williamson's sapsucker 









Yellow-rumped warbler 










Total (all birds) 










Total (cavity nesters) 










Total (other birds) 










and to improve plant vigor through decreased 
competition from spruce and reduced browsing (for 
a few years) by moose. 

Cavity-nesting Birds Respond to Snag Removal. 

— Dead trees, commonly referred to as "snags," 
occur naturally in forests as a result of lightning, 
fire, disease, insects, parasites, and other causes. 
Many wildlife species use snags for nesting, 
roosting, lookout perches, food storage, and 
feeding. Snags are a necessary component of the 
forest ecosystem to some beneficial cavity-nesting 

Results of a study in the ponderosa pine type on 
the Apache-Sitgreaves National Forest in Arizona 
indicated that removal of ponderosa pine snags can 
be detrimental to some species of cavity-nesting 
birds. The study area consisted of three plots. Trees 
were harvested from two of the plots (A and B) 
within a timber harvest unit while the third (C) 
served as a control. Conifer snags were removed 
from Plot A and an effort was made to retain all 
snags in Plot B. Fourteen aspen snags remained on 
Plot A after the timber harvest, which provided nest 
sites for some birds. The greatest decline from 
preharvest numbers occurred in violet-green 
swallows and pigmy nuthatches, which nested 
mostly in ponderosa pine snags. Cavity-nesting 
birds declined by 48% in Plot A, whereas both the 
snag retention area (Plot B) and the control (Plot C) 
had increases of 42 and 48%, respectively. Birds 
that normally used either dead or live aspen for nest 
sites (mountain chickadees, flickers, and hairy 
woodpeckers) showed little response to the removal 

of ponderosa pine snags. 

Although birds nested in both dead and living 
aspen trees, only the dead portions of live 
ponderosas were used. Of the 93 cavity nests found 
on the study area, 66% were in ponderosa pine 
snags and 11% were in dead portions of living 
ponderosa pine. A preference was shown for snags 
over 19 inches dbh and for snags that retained over 
40% of the bark. Snags 15 to 75 feet tall received 
nearly equal use as nest sites, but a significantly 
higher use was made of snags over 75 feet tall. 

Clear-cut Burns Change Small Mammal 
Populations in the Northern Rockies. — In the 
northern Rocky Mountains, fire is applied annually 
to 30,000 acres of national forest to reduce logging 
slash and provide bare soil seedbed necessary for 
successful establishment of many species of 
conifers. Animal response to this practice is not 
only important as basic ecological knowledge but is 
also necessary for understanding the effects of 
rodents on establishment and survival of tree seed. 
Populations of small mammals are currently being 
studied in Montana's Flathead and Lolo National 
Forests to determine patterns of animal succession 
on experimentally burned areas, as part of a U.S. 
Forest Service study of fire as a forest management 

Small mammal populations were sampled 
annually in fall before and after logging and 
burning in two similar stands of mature larch, 
spruce, and Douglas-fir, 120 miles apart. Results 
from the two sites point to similar population 
trends during eight postfire years ( 1 968-75) of snap- 


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General view of clear-cut in Douglas-fir, western larch, and lodgepole pine after slash burn, Flathead National Forest, 
Montana. Photo by C. H. Halvorson. 

trapping one area, and six postfire years (1970-75) 
of livetrapping the other. Redback voles were most 
common (3 to 13 per 100 trap nights) in unlogged 
stands, followed by chipmunks (3 to 6 per 100 trap 
nights); deer mice were scarce (0.7 per 100 trap 
nights) in these stands. 

Rodent abundance the 1st year after fire was low 
except for deer mice. Deer mice increased even in 
the burn year and remained the most abundant 
species on all disturbed areas (5-13 per acre). By the 
second postfire year, burn populations were higher 
than those in timber. In general, the most severely 
burned site — a hard-burned south slope — initially 
showed a greater number of animals than other 
burns, but only one species (the deer mouse) was 

present. A very light burn had the fewest animals 
for 2 years — only four species (deer mice, 
chipmunks, long-tailed voles, and shrews). By the 
fourth postfire year (1974), the populations of the 
lightly burned plot had surpassed those of the 
severe burn and continued to increase; an average 
of 16 rodents per acre occurred in 1974 and 1975. 
Redback voles did not survive on either burn except 
at forest edges, whereas chipmunks were scarce at 
first but showed a gradual increase with developing 
plant cover. 

When two clear-cuts were left unburned, rodent 
numbers were still very low after 6 years; however, 
by the 8th year, the largest variety and numbers of 
small mammals on snap-trapped plots (22 per 100 


trap nights) occurred on these slash areas. Deer 
mice, long-tailed voles, heather voles, shrews, 
chipmunks, and redback voles were caught there. 
Unburned and poorly burned slash are persistent 
fuel and silvicultural problems in the region and 
appear to provide excellent rodent habitat as time 
passes. A wildfire area where dead trees were left 
standing was intermediate in rodent numbers (15 
rodents per 100 trap nights) between unburned 
slash and clear-cut burns. Deer mice again were 
most common. Wildfire plots had best germination 
and survival of conifer seedlings among all habitats. 

The important knowledge gained from these 
long-term studies shows that the deer mouse, an 
important consumer of tree seeds, thrives in several 
types of purposely and accidentally disturbed forest 
habitat. Rodent populations may be more 
abundant and diverse over a longer time span on 
areas with poorly burned or unburned slash than on 
hard burns. Further study will determine the point 
at which rodent numbers and species composition 
become similar to those in uncut forests. Results 
will also be correlated with plant succession and 
tree establishment in this cooperative research 

Brewer's Sparrow Most Abundant User of 
Sagebrush Rangeland in South-central Wyoming. 
— Land management agencies, industrial users, 
and private landowners have converted thousands 
of acres of big sagebrush rangelands to croplands, 
grasslands, and mine spoils through the years, by 
chemical and mechanical means. The potential 
influence of continuing modification of the 
sagebrush habitat on native animal populations is a 
matter of concern to those interested in the welfare 
of wildlife. 

In 1968, a cooperative study was started with the 
U.S. Bureau of Land Management and the U.S. 
Forest Service in south-central Wyoming to 
determine the effects of the conversion of a stand of 
big sagebrush to herbaceous vegetation with 2, 4-D 
herbicide. Research emphasis was placed on soil 
water, streamflows, forage production, vertebrate 
animal populations, aquatic insect populations, 
algae, and terrestrial insect populations. Measure- 
ments of water yields, forage, and animal 
populations on two sagebrush drainages were 
started in 1969 and were continued through 1975. 
Herbicide treatment to kill sagebrush on one of the 
two drainages was completed in May of 1976. 

Bird populations were inventoried annually from 
1971 to 1975 on each of the two drainages. Plots 
were visited three or six times each during June, and 
cluster sightings or singing points of each species 

The Brewer's sparrow is the most abundant of the four 
species of birds commonly netting in dryland sagebrush, 
south-central Wyoming. Photo by M. H. Schroeder. 

were assumed to indicate the number of breeding 
territories for that species on square 40-acre plots. 

During the pretreatment period, 36 bird species 
used the sagebrush habitat and the small stream 
and meadow bottoms within it. Four species 
(Brewer's sparrow, vesper sparrow, sage thrasher, 
and the green-tailed towhee) consistently nested in 
the dryland sagebrush. The Brewer's sparrow, with 
an estimated average annual population of 72 birds 
per 1 00 acres, was the most abundant species on the 
untreated rangeland. It was dependent on 
sagebrush plants for its nest site and brood-rearing 
activities. The ground-nesting vesper sparrow was 
second in abundance, with an estimated average 
annual population of 40 birds per 100 acres. Sage 
thrashers and green-tailed towhees, both brush- 
nesting species, averaged an estimated 10 birds per 
100 acres. 

All available evidence indicates that the presence 
of living sagebrush cover is critically important to 
the maintenance of a Brewer's sparrow population. 
Sagebrush provides both structural support and 
protective cover to the bird's nest and young. After 
brush has been killed by treatment with herbicides, 
there is little likelihood that the remaining skeletal 
brush stems will provide suitable cover for nest site 
selection by this species. 


Biological Survey of the Tres Marias Islands, 
Mexico. — A joint team of biologists from the 
Direccion General de la Fauna Silvestre of Mexico 


and the Laboratory visited the Tres Marias Islands 
during March 1976. The only previous extensive 
work on the Islands was by a U.S. Bureau of 
Biological Survey team headed by E. W. Nelson 
and E. A. Goldman in 1897. The recent expedition 
revealed changes that have occurred in the flora and 
fauna of the Islands during the past 80 years. 

Greatest changes were noted for the largest 
island, Maria Madre, where the Government of 
Mexico has maintained a penal colony for many 
years. Extensive logging and clearing of forest for 
agriculture have changed the landscape considerably. 
A small frog appears to have been extirpated, 
possibly due to habitat changes near freshwater 
sources where it once occurred. An edible turtle no 
longer occurs on the island, and a large iguanid 
lizard has been reduced in numbers, apparently by 
human consumption. 

In 1897, the most common small mammal in the 
Islands was an endemic subspecies of deer mouse 
(Peromyscus boylii madrensis). In that year, the 
black rat (Rattus rattus) was found only in 
association with the few houses on Maria Madre. 
Now, the black rat is the most common small 
mammal and is found throughout Maria Madre 
and Maria Magdalena. The deer mouse is scarce on 
Maria Madre at present, and despite extensive 
trapping, none were found on Maria Magdalena. 
However, they are still common on Maria Cleofas 
and San Juanito, where black rats are absent. 
Furthermore, an endemic rice rat, known only from 
a single locality on Maria Madre, is no longer found 
there, and black rats are abundant at that locality. 

Status of the Mexican Freetail Bat. — Recent 
observations indicate that drastic declines have 
occurred in populations of the Mexican freetail bat 
(Tadarida brasiliensis). The size of the summer 
population at Carlsbad Caverns, New Mexico, 
declined from an estimated 8.7 million in 1936 to 
200,000 in 1973, and the population at Eagle Creek 
Cave, Arizona, dropped from about 25 million in 
1964 to 600,000 in 1970. Concern about the decline 
prompted the National Park Service to contract 
with the Laboratory for a 4-year study (June 1973- 
June 1977) to determine the factors causing the 
decrease in populations of this bat. Although the 
major portion of our data was collected at the 
maternity colony located in Carlsbad Caverns, our 
study included colonies in Arizona, Texas, 
California, and Mexico. 

By use of high-speed motion pictures and still 
photographs, a useful and accurate technique was 
developed for estimating the size of populations of 
this bat. This technique was used for the first time 

on September 1, 1973, at Carlsbad Caverns. The 
total number of bats that left the cave that evening 
was calculated to be 218,153. This photographic 
technique was used during the remainder of the 

The ontogeny of fat deposition and depletion in 
the freetail bat was investigated. Organochlorine 
pesticides are stored in body fat, and this may 
provide a mechanism for preventing toxic effects. 
Therefore, in order to understand the potential 
effects of pesticides on bats, it is important to know 
the body fat cycles of the young in terms of both 
deposition and depletion. This study showed that 
body fat in bats from Carlsbad Caverns increases 
steadily from birth until the young begin to fly, then 
fat reserves are gradually used until fall migration. 

The amount of pesticide stored in body fat was 
greatest in flying young from the Carlsbad Caverns. 
Flying young from Eagle Creek Cave, Arizona, 
Bracken Cave, Texas, and Newman Bridge, 
California, had similar chemical body burdens. As 
flying young from migratory populations mature at 
their maternity roosts, they grow, utilize body fat, 
and excrete body pesticides, whereas flying young 
from nonmigratory populations deposit fat and 
accumulate pesticides as they grow. 

The hypothesis that the critical stage in the life 
cycle of the Mexican freetail bat may occur during 
the initial migratory flight was tested. The initial 
flight is the time when rapid mobilization of fat 
releases toxic residues that may reach the brain in 
lethal or detrimental amounts. By simulating in the 
Laboratory the fat mobilization that occurs during 
migratory flight, it was demonstrated that 
significant increases in organochlorine residues can 
occur in the brain and cause symptoms of poisoning 
in young bats. 

Status of the Indiana Bat. — Contract research 
on the Indiana bat (Myotis sodalis) was completed 
during 1976. This work consisted of a study of the 
summer habitat and ecology of this endangered bat, 
a winter census of the species, and associated 
investigations. The number of living Indiana bats 
has declined 34% in the last 1 5 years. Declines in the 
two major breeding populations have been 73% in 
Kentucky and 8% in Missouri. Winter habitat 
consists of caves and mines, with suitable sites 
restricted to those that have cool and stable 
temperatures all winter long. These roosts typically 
have microtemperatures of 4° to 8°C, enabling the 
bats to maintain such a low metabolism that their 
fat will last until spring. Causes of the decline are 
natural catastrophes (flooding and freezing in 
caves), disturbance by biologists and caving 


enthusiasts, and destruction of winter and summer 
habitat. Loss of 60,000 bats at one cave is 
attributable mainly to human disturbance. About 
half of the total decline resulted from habitat losses 
when structures were built at cave entrances. These 
structures interfere with cave thermodynamic 
processes and make roosts too warm for bat 
survival. These habitats can be restored, and the 
decline may be reversed. 

Rates of survival of Indiana bats were calculated 
from recaptures of bats marked in cohorts of 
unknown age. Survival rates are high for 10 years 
after marking in females and 6 years in males. Both 
sexes can live as long as 13.5 years. 

Adulthood is characterized by two survival 
phases. The first is a high and apparently constant 
rate from 1 to 6 years after marking. Annual rates of 
survival in this phase are 75.9% for females and 
69.9% for males. The second is a lower and again 
constant rate after 6 years, with annual rates of 
66.0% for females up to 10 years and 36.3% for 

That some differential survival occurs between 
the sexes indicates distinct life histories with 
different patterns of mortality. For example, adult 

males do not occupy nursery roosts. They also 
remain active later in autumn than females because 
many of them stay outside the caves to breed 
whereas females enter hibernation soon after they 
arrive in migration. 

High survival under normal circumstances shows 
that the species' endangerment cannot be attributed 
to intrinsically poor performance in normal 
environments. Instead, the failure of the Indiana 
bat is intolerance of environments degraded by 

During summer, Indiana bats live in small 
colonies consisting of adult females and their 
young. These nursery populations occupy hollows 
and cracks under bark of dead trees. Feeding 
habitat is restricted to air space near the leaves of 
creekside and floodplain trees. On a one-for-one 
basis, the loss of one summer colony is less 
detrimental to the species than loss of one winter 
colony, because a typical winter colony contains 
many more animals. However, land clearing by 
private landowners and land-use changes made by 
numerous State and Federal agencies are causing 
serious losses of summer habitat. 

Cooperative Research Unit Program 


The Cooperative Research Unit Program is 
supported by the U.S. Fish and Wildlife Service 
and by the game and fish agency and land grant 
university in the State where each Unit is located. 
The Wildlife Management Institute is an additional 
cooperator for Wildlife Units. The Program began 
with the activation of the Iowa Cooperative 
Wildlife Research Unit in September 1935. The first 
Fishery Unit was activated in 1962 at Utah State 
University. Twenty-five Fishery Units have been in 
operation since 1971 and 20 Wildlife Units since 
1972. In 1973 the two Unit programs were merged 
into one, administered by the Division of 
Cooperative Research. 

The objectives of the Cooperative Research 
Units, in order of priority, are fish and wildlife 

research, training at the graduate level, and 
extension service. Unit direction is provided by a 
Coordinating Committee composed of repre- 
sentatives from each cooperating agency. The 
Committee provides counsel and plans the long- 
term program to serve the mutual needs of the 
cooperators. Day-to-day operation is the respon- 
sibility of the Unit Leaders and the Assistant Unit 
Leaders, who are employees of the U.S. Fish and 
Wildlife Service. The Units are headquartered on 
the campuses of the cooperating universities, which 
provide expertise in related scientific fields; office, 
laboratory, and storage space; secretarial service; 
and utilities. All cooperators contribute funds and 
equipment to the Units, and additional research 
funds are obtained from various sources as grants 
and contracts. The Leaders and Assistant Leaders 
are granted full faculty status by the cooperating 


universities and thus they are qualified to advise 
and direct graduate students and to teach formal 
courses. In the field of extension service, Unit 
personnel organize and participate in workshops 
and training meetings and provide technical fish 
and wildlife expertise as needed. Each year, Unit 
personnel publish many technical and general 
papers on fish, wildlife, and related subjects. 

During the fiscal year 1975-76 (15 months in 
length due to the change in Federal fiscal years), 
personnel of the Fishery Units conducted 352 
research studies, 129 of which were completed. 
Ninety-seven of the 323 studies carried out by 
personnel of the Wildlife Units were completed. 
These studies and other activities resulted in 116 
technical and general publications from the Fishery 
Units and 127 from the Wildlife Units. Papers 
presented at meetings totaled 77 for the Fishery 
Units and 62 for the Wildlife Units. The following 
table summarizes training activities at the 45 Units 
during 1975-76: 







Students in program 





Degrees granted 





Employment 1 

Fish and wildlife biology 





Other biology 



Education continued 



Peace Corps 



Miscellaneous and unemployed 




'Includes students who accepted employment before completing all 
degree requirements. 


Alabama. — Pond culture of many species is 
hindered by early maturity and frequent spawning 
that result in overpopulation and stunted growth. 
One way to control excessive reproduction is to 
develop monosex fish by chemically induced sex 
reversal. We have repeatedly produced all-male 
populations of tilapia with androgen-treated food. 
Present efforts are directed toward production of 
monosex female populations to be used in breeding 

Three naturally occurring estrogens (estriol, 
estrone, and 17 B-estradiol) were fed to 8- to 11 -mm 
fry at 30, 60, and 120 ug/g diet for 3 or 5 weeks. 
Tilapia grown to maturity in ponds were harvested 

and sexed. External appearance of the sexually 
dimorphic urogenital papillae was compared with 
the condition of the gonads as determined by 

Estrogen treatment neither affected survival nor 
altered growth of experimental fry. Gonadal 
examination revealed no deviation from the 
expected 1:1 sex ratio, but significantly greater 
numbers of individuals in all treatment groups had 
female-like papillae. A greater proportion of 
atypical males occurred at the higher levels of 
estrogen dosage and in the longer treatment period. 
No atypical males were in the control groups. 

Additional testing is in progress with more 
potent estrogens and with increased duration of 
treatments. Estrogen-induced sex reversal of 
homogametic males to functional females will 
permit breeding to yield all-male progeny. 
Chemical treatment would be necessary only to 
replenish brood fish. 

Arizona. — The diel feeding of brook trout was 
observed in relation to invertebrate stream drift and 
benthos during seven 24-hour sampling periods, 
May to September 1975, in the East Fork of the 
Little Colorado River in the White Mountains of 

A diel difference was found in the feeding of 
brook trout. During the day trout fed efficiently on 
available foods, but at night their feeding efficiency 
decreased. The result was a high rate of consumption 
of invertebrates active during the day and a low rate 
for those active at night. Trout were nonselective in 
their use of drifting invertebrates. 

Different factors controlled the availability of 
aquatic and terrestrial invertebrates to trout. This 
finding has significant implications for trout stream 
management. It appears difficult to increase 
significantly the availability of aquatic invertebrates, 
but the availability of terrestrial invertebrates 
depends largely on their abundance near trout 
streams. Poor land-management practices along 
streams could adversely affect terrestrial insect 
populations, on which brook trout rely for a large 
percentage of their food. 

California. — Our research activities concerned 
primarily the ecology of northern coastal streams 
and reservoirs, and estuarine and coastal marine 
biology. Northern California streams are located 
largely in redwood forests, and the watersheds are 
now undergoing all stages of logging; all streams 

Annual coordinating meeting at a Unit. Each Unit is administered by a Coordinating Committee representing the State 
conservation agency, the State university, the U.S. Fish and Wildlife Service, and the Wildlife Management Institute 
(Wildlife Units only). Photo by S. Leen. 


are important salmonid producers. Humboldt Bay 
is the most important aquatic habitat in the 
immediate area. The Bay area is relatively 
undeveloped but many agencies and private groups 
are interested in its developmental possibilities. 

Studies of the Pacific herring have facilitated the 
management of commercial herring fisheries along 
the northeast Pacific Coast. When herring move 
into shallow inshore waters to spawn they become 
vulnerable to gill nets and haul nets. Fishery 
managers must know the size of the spawning stock 
in order to regulate the commercial harvest. 
Humboldt Bay has supported a bait and commercial 
herring fishery for several years, but no effort has 
been made to estimate stock size, which in turn 
could be used for fixing harvest quotas. Herring 
spawn in Humboldt Bay during December through 
March. Size of spawning stock, estimated from egg 
deposition, was 372 tons for the 1974-75 winter and 
241 tons for the 1975-76 winter. Adult spawners 
were 2 to 1 1 years old, but ages II and III accounted 
for 57% of the estimated stock. Most spawning 
occurred in north Humboldt Bay even though 
eelgrass, the preferred spawning substrate, was less 
dense there than in south bay. North bay receives 
more fresh water than south bay, and because low- 
saline water stimulates spawning, this difference 
could account for the greater utilization of north 

Colorado. — Studies of the bottom sediments of 
Twin Lakes, Colorado, have indicated that a 
dramatic change in the microscopic plant life in the 
upper lake occurred with the onset of extensive 
mining developments on the watershed and 
increased human settlement in the area about 100 
years ago. Changes in the plant community of the 
upper lake are still reflected in its sediments as it 
continues to act as a nutrient trap on the two-lake 

Studies of populations of lake trout and opossum 
shrimp before completion and operation of the Mt. 
Elbert pumped-storage hydroelectric generating 
plant at Twin Lakes indicated that both species may 
undergo entrainment and heavy mortality during 
plant operation. Increased turbulence in the lake, 
resulting from operation of the plant, is likely to stir 
up loosely compacted bottom sediments and 
increase turbidity, thereby disrupting the currently 
well-established opossum shrimp-lake trout food 

Snake River cutthroat trout tended to segregate 
themselves from other trout species in small lakes. 
They exhibited differences in food habits, growth, 
survival, spatial distribution, and angling vulner- 

ability. These observations suggest that the Snake 
River cutthroat trout can improve fishing quality 
by filling an otherwise unoccupied niche in small 

Georgia. — Three small trout streams (Dick's, 
Tuckaluge, and the Chattahoochee) in north 
Georgia were poisoned by the State Fish and Game 
Division in 1 970 to remove reproducing populations 
of rainbow and brown trout. These streams were 
later restocked with brook trout from headwater 
streams of adjacent drainages. During this study, 
April 1975 to April 1976, brook trout in each of the 
three streams grew very slowly. Total tissue growth 
was 0.32, 0.36, and 0.72 g offish per square meter of 
water per year for Dick's, Tuckaluge, and the 
Chattahoochee, respectively, The Chattahoochee 
has significantly better trout habitat (more rubble, 
boulders, and riffles) than the other two streams, 
which most likely explains its higher productivity. 
These data suggest that to maintain quality fishing, 
anglers should take only small numbers offish from 
these streams. 

Bluegills were exposed to various combinations 
of toxaphene and methyl parathion in a static 
system and in a specially designed flow-through 
system. There was evidence of a synergistic effect of 
the two insecticides in tests of acute exposure. In 
tests of chronic exposure, high concentrations of 
methyl parathion (268 ppb) caused some bone 
deformities. There was no evidence that either 
insecticide or any combination of the insecticides 
affected growth. 

Fish kills have been observed in ponds adjacent 
to fields sprayed with toxaphene and methyl 
parathion. Three days after one of these kills was 
reported, the concentrations of toxaphene and 
methyl parathion in the water were both about 6 
ppb (roughly twice the concentration of toxaphene 
that killed fish in our laboratory studies). 

Hawaii. — Streams, Hawaii's most abundant 
type of inland water environment, have been 
seriously degraded by socioeconomic growth. One 
of several stream-oriented studies is a statewide 
inventory, the first part of a three-phase project to 
determine effects of channelization on native fauna. 
Among the five largest islands, 330 perennial 
streams were tallied. Oahu, the most populated 
island, has the lowest abundance of native stream 
animals, and more than half of its 54 streams have 
significant channel alterations. Artificial channels 
cause elevated water temperatures, which — 
together with changes in food and shelter — favor 
the proliferation of exotic fishes like guppies and 


Opae kalaole (Atya bisulcata) is one of the most abundant 
native Hawaiian stream animals. This small (<5 cm long) 
shrimp prefers precipitous streams where it filter-feeds on 
seston particles in swift current by means of five bristles at 
the tips of its legs. The Hawaiian name means "spineless 
shrimp." Hawaii Cooperative Fishery Research Unit photo. 

Four Unit studies dealt with the biology and 
taxonomy of unique native aquatic invertebrates. 
Opae kalaole, a small endemic stream shrimp often 
netted for food and bait, heretofore has been 
classified as two species in different genera. 
Laboratory breeding trials and examination of 
1,255 specimens from 15 streams indicated that the 
two shrimps are a single dimorphic species properly 
identified as Atya bisulcata. Favorable development 
of larvae in saline water and ecological data from 
streams demonstrated that Atya is diadromous; 
genetic uniformity throughout the archipelago is 
maintained by marine dispersal of larvae. 

Research on anchialine pools at Cape Kinau, 
Maui, concluded with an evaluation of their 
aquatic plant communities. Representing an 
unusual type of aquatic ecosystem, these rocky 
coastal pools consist of brackish groundwater in 
geologically recent lavas and are connected to the 
ocean only through subterranean interstices. They 
are noted for peculiar shrimp and mollusk fauna. 
Four types of vegetational communities were 
identified: three were crusts and mats of filamentous 
algae dominated by Lyngbya and Scytonema; the 
fourth, widgeon grass with associated algae, 
occurred only in pools with sediment. 

Concern over the exploitation of reef fishes by 
collectors for the aquarium industry prompted 
study of the biology of an endemic butterflyfish, 
Chaetodon miliaris. The fish was found to be 
ubiquitous, highly fecund (100,000 eggs per 
female), and omnivorous, with a predilection for 

Chaetodon milianis, an endemic yellow-and-black 
butterflyfish, is common on shallow Hawaiian reefs where 
it is collected extensively for the aquarium trade. Its 
abundance, fecundity, and broad habitat requirements 
suggest that this species is not presently in danger of 
exploitation. Hawaii Cooperative Fishery Research Unit 

zooplankton. These factors and the known 
presence of stable populations in various types of 
reef habitat suggest that the species is not in 
immediate danger of overexploitation. 

Idaho. — Effects of coarse granitic sediment on 
abundance, distribution, growth, and behavior of 
juvenile salmonids and abundance of aquatic insect 
drift in the central Idaho Batholith were assessed by 
adding sediment to artificial and natural stream 
channels. Densities of juvenile steelhead and 
cutthroat trout and chinook salmon in artificial 
stream channels decreased as sediment was 
increased. The density of insect drift was not 
affected by the addition of sediment to riffles in 
artificial streams, but Diptera increased in relative 
abundance. Addition of sediment reduced fish 
densities by causing a loss of cover and pool 
volume, but insect abundance was not significantly 
changed. In the natural streams, fish density 
correlated best with cover and density of insect drift 
whereas density of insect drift correlated best with 
riffle size and percentage of sediment in riffles. 

Effects of closure to angling on cutthroat trout 
populations in the St. Joe River, Idaho, and its 
tributaries were assessed by evaluating species 
composition and the abundance and movements of 
cutthroat trout in closed tributaries and in 
tributaries open to angling. Closure to angling 
resulted in larger numbers of juvenile cutthroat 
trout and of those of catchable size because survival 
rate increased, whereas streams open to angling 
showed no significant change in abundance of 


A bank stabilization structure. Even at low flow the 
structure, although not aesthetically beautiful, provides a 
scour hole at its base for fish shelter. Similar structures of 
rock are preferred from a fishery standpoint. Photo by R. V. 

Metal and wood jetties used to protect bridge abutment on 
the Des Moines River, Iowa. Structure provides a scour 
hole and cover for fish even at low flow. Rock is superior as 
a construction material because it provides substrate for 
invertebrate production. Photo by R. V. Bulkley. 

trout. Most cutthroat trout in tributaries retained 
limited home ranges and remained in their natal 
streams. Of more than 6,200 salmonids tagged in 
tributaries, 688 cutthroat trout were recovered, 610 
of them in the tributary in which they were tagged. 
Tributaries also contained populations of migratory 
cutthroat trout. Progeny of the migratory stock 
remained in streams for 1 or 2 years before 
migrating. Because most of the migratory cutthroat 
trout we observed were in the lower sections of the 
tributaries, the increased abundance resulting from 
closure to angling presumably increased the 
number that entered the St. Joe River. Cutthroat 
trout also increased in abundance in upper sections 
of the closed streams but few of these trout 
migrated to the St. Joe River. Tributaries play an 
important role in the production of cutthroat trout 
for the trout fishery in the St. Joe River. 
Management alternatives — including bag limits, 
size limits, shortened angling seasons, and periodic 
stream closures — could be used to increase the 
stock of migratory fish and to improve the fishery 
for resident cutthroat trout in tributaries. 

Iowa. — Studies conducted from 1973 to 1976 
under five subprojects resulted in six reports 
providing information on channelization and its 
effects on stream life. Channelization of natural 
waterways has been an integral part of drainage and 
flood-control projects in Iowa since the late 1800's. 
Over 1,000 miles, but probably less than 3,000 
miles, of streams large enough to support year- 
round fish populations have been lost in Iowa 
through stream channelization. Channelized 
streams vary in quality of habitat; some continue to 
degrade, but others contain fish populations similar 
in abundance and composition to those in natural 

Although the sinuosity index (horizontal 
straightness of the stream bed) correctly identifies 

Rock jetties installed to protect a bridge provide shelter for 
fish on the Skunk River, Iowa, even at low-flow periods as 
shown here. In many streams with silt bottoms, these 
structures provide the major source of hard substrate for 
production of certain fish-food organisms. Photo by R. V. 

previously channelized sections of streams, it does 
not accurately reflect the density of invertebrate 
drift nor fish abundance. Riffle pools caused by 
trees or snags can partly replace pools lost when 
stream beds are straightened. In streams with rocky 
substrate, fish abundance may be better related to 
stream gradient. Oxbows cut off from the main 
channel gradually fill with sediment and contain 
fewer species and numbers of fishes. 

Structures for stream-bank protection that 
extended far enough into the stream channel to 
produce permanent scour holes encouraged fish use 
by providing cover and fish-food substrate. 

Louisiana. — Seventeen research projects were 
undertaken within the general subject "Limnological 
Survey of the Atchafalaya Basin." This survey was 
designed to yield data for use in environmental 
assessment of flood-control projects in overflow 
habitats. Subprogram subjects included Inland 
Fisheries, Coastal Anadromous Fisheries, Habitat 


Preservation, Stream Alteration, and Wetland 
Inventory. Mathematical models were developed 
that relate variation in abundance of key micro- and 
macro-zooplankton to aquatic habiat types and their 
respective physicochemical characteristics. The 
degree and direction of habitat succession in the 
lower Basin is now estimable, as are seasonal 
variations in water quality and the biota 
characteristic of phytoplankton, zooplankton, 
benthic, and fish communities in the various 
habitats. Our final report should prove useful in 
developing a plan for flood control that will protect 
the Basin's fish and wildlife resources. 

Many fishes, as well as shrimp and crabs, spawn 
in the Gulf of Mexico. Later, the young use coastal 
marshes as "nurseries," but there is little 
information on the timing of their return to the 
Gulf. Therefore, we installed a trap on a marsh 
outlet to study emigration of the juvenile Atlantic 
croaker, an economically important fish. Catches 
conclusively demonstrated a continual "bleeding 
off of the large juveniles from nursery to the Gulf. 
This observation contradicts some statements in 
the scientific literature (based on circumstantial 
evidence) that young-of-the-year leave the nursery 
as a group. Evidence of several population 
"turnovers" per year indicates that these coastal 
marshes are even more important to the maintenance 
of flourishing populations of marine fish than 
previously realized. 

Maine. — Overwinter survival of fin-clipped and 
unmarked brook trout was evaluated in a reclaimed 
pond. Ten thousand fall fingerlings were divided 
into 20 treatment groups, marked by single or by 
multiple fin excisions, and stocked in October 1974. 
Analysis of returns from creel and trap-net 
sampling in April and May 1975 indicated that: (1) 
survival of unmarked, unanesthetized trout was 
significantly higher than that of marked fish, (2) 
survival of trout with multiple fin excisions was 
lower than that of fish with single fin excisions, (3) 
removal of the adipose fin was least detrimental to 
survival, and (4) removal of a pectoral fin was no 
more damaging to the fish than removal of a ventral 
fin. Spring recovery indicated equal vulnerability 
among the treatment groups to both sampling 
methods. Overwinter survival was low for all 
groups. This study indicates that care should be 
taken when management recommendations are 
made on the basis of survival rates estimated from 
fin-clipped brook trout. 

A search of the literature revealed that sterility in 
fish could be induced with irradiation from X rays 
or radioactive isotopes. Generally, irradiation 

caused side effects and sterility was temporary. 
Chemosterilants and high dosages of hormones 
disrupt reproductive function, but fertility returns 
after the withdrawal of treatment. 

In a study of hormonal mechanisms controlling 
reproduction in fish, corticosteroids caused 
breakdown of ovarian membranes and connective 
tissue and neurohypophysial hormones produced 
contraction of ovarian smooth muscle in the guppy. 
Live-bearers and oviparous fish thus appear to have 
similar hormonal control of the reproductive 

Massachusetts. — Most of our present knowledge 
of insect communities in North American streams 
has been incidentally acquired during fish food 
studies, despite the economic importance of stream 
insects in sustaining fish populations. Research was 
conducted along a 13-km woodland stream in 
western Massachusetts to determine diversity and 
emergence patterns of aquatic insects, drift 
distances of caddis fly larvae, and productivity of 
the insect community living on stones. After 2 years 
of extensive sampling of adults, 45 species of stone 
flies, 50 species of mayflies, and 120 species of 
caddis flies were collected from the stream. 
Comparing these collections with collections of 
immatures indicates that stream insect communities 
are more diverse than benthic sampling indicates. 
The microhabitats of uncommon and rare species 
are usually overlooked during routine stream 

Marking of caddis fly larval cases with acrylic 
pigment and subcutaneous fish tags showed 
considerable downstream displacement of larvae. 
Over a 5-week period, most larvae drifted 0.4 to 0.7 
km downstream from their release site; a few drifted 
as far as 1.5 km. High streamflow after a rainstorm 
dramatically increased the rate and distance of 
downstream displacement. Upstream flight of egg- 
bearing females appeared to compensate for this 
larval drift. 

Estimates of the productivity of stone-inhabiting 
fauna ranged from 3.9 to 4.3 g/m 2 (dry weight) for 
two consecutive years. Mayflies were by far the 
most important secondary producers in the 
community. Algae and detritus-feeding insects 
contributed 88% of the productivity and carnivorous 
species, 12%. Low insect productivity in conjunction 
with high faunal diversity is probably typical of 
oligotrophic streams throughout the United States. 

Missouri. — Excessive growth of submerged 
aquatic plants adversely affects recreational 
pursuits and fish production in many ponds and 
small impoundments. The effect of grass carp on 


the growth of aquatic plants, on water quality, and 
on the production of glass shrimp, fathead 
minnows, and bluegills was evaluated in a series of 
14 small ponds. The reduction of aquatic plants by 
grass carp reduced the problem of oxygen 
depletion, prevented adverse changes in pH and 
alkalinity, increased reproductive success of 
bluegills, and had no detrimental effect on 
production of fathead minnows and glass shrimp. 
Biological control appears to offer economic and 
ecological advantages over chemical control in 
some impoundments. 

The redear sunfish was evaluated in ponds, where 
it was substituted for the bluegill, and in small 
impoundments as an additional species with 
largemouth bass, bluegills, and channel catfish. 
Missouri is an extension of the natural range of the 
redear sunfish, which is essentially a southern 
species. A mild January in central Missouri can 
enhance the survival of the young in ponds, and a 
strong year-class can in turn improve survival of 
young bass and growth of adult bass. However, 
mild winters and strong year-classes of redear 
sunfish are uncommon at this latitude. Nevertheless, 
this species is a valuable addition to the fish 
community in impoundments with favorable 

The structure and dynamics of bass populations 
were evaluated in 38 ponds in the central States. 
The analyses indicate that poor reproduction is 
usually associated with a relatively low density of 
adults. Fishing quality was unsatisfactory in most 
of the ponds because there were relatively few bass 
longer than 30 cm ( 1 2 inches). A model for balanced 
populations indicates that for the length-frequency 
distribution of the bass stock — all bass larger than 
20 cm (8 inches) — 45 to 65% should be longer than 
30 cm. This balance may best be achieved by a 
length limit that protects all bass 30 to 40 cm ( 12 to 
16 inches) long. The threefold intent of this 
regulation is to permit the harvest of surplus young 
bass, to allow the catch and release of bass of 
quality size, and to increase the harvest of large 
bass. The logic behind the regulation is to protect 
these important predators for the 25% of their 
possible life-span when they are most likely to gain 
weight. A balanced distribution has been achieved 
on the first lake where this regulation was applied. 

Montana. — Stream morphology and game fish 
populations of the St. Regis River were studied in 
1973-75 to determine the effects of the channelization 
during highway and railroad construction. 
Population estimates were made by electrofishing 
methods in stream sections that were unaltered, 

recently altered, recently altered but with 
"mitigating" structures added, or altered several 
years ago. Each study section was mapped. 
Mitigating structures (jetties and rock clusters) 
provided fish habitat comparable to that in 
unaltered sections. Fish populations in new 
channels stabilized within about 1 year. Populations 
in "old" altered sections (with no mitigations) failed 
to recover the levels in unaltered sections. For 
aesthetic reasons, fishermen preferred unaltered or 
partly altered sections to those that had been 
channelized. The number of pools per stream 
section, as measured by pool-riffle periodicity, 
provided the closest correlation to changes in trout 

The fishery of Hyalite Reservoir was known to be 
substantial but was unmeasured. A partial creel 
census was conducted during the summers of 1974 
and 1975 to estimate the yield of this fishery. Of the 
estimated 3,419 fish taken from the reservoir during 
the 2 years, about 90% were cutthroat trout. About 
72% of the harvested cutthroat trout were hatchery 
fish, and 28% were wild. In 1975, only 22 wild fish 
and no hatchery fish were taken in the spawning run 
of cutthroat trout, and no cutthroat trout fry 
moved from the spawning stream into the reservoir. 
As a result of this study, 20,000 cutthroat trout fry 
from a wild strain have been introduced into the 
spawning stream in an attempt to establish a new 
naturally reproducing population. 

Increasing demands for water will cause future 
alterations in the flows and water quality of 
Montana rivers. During 1974 and 1975, aquatic 
insects and water quality were studied at six riffles 
over a 300-km reach of the Musselshell River to 
obtain useful information before alterations 
occurred. Choroterpes, Baetis, Simuliidae, and 
Hydropsyche made up 80% of the organisms taken 
on modified artificial substrates. Dissolved oxygen, 
pH, temperature, conductivity, turbidity, calcium 
and total hardness, and chloride and sulfate levels 
at each station were recorded. Changes in aquatic 
insect communities and water quality, caused by 
future alterations of the river, can be assessed by 
reference to these data. 

New York. — Waterborne commerce of the 
United States exceeds 1.5 billion tons per year. The 
rapid filling of our harbors and navigation channels 
with alluvial sand, silt, and clay necessitates 
dredging 300 million cubic yards of sediment each 
year. Sediments dredged from many areas are 
contaminated with heavy metals, pesticides, 
petroleum wastes, and other pollutants, and the 
resuspension and distribution of these sediments 


Dorsal and lateral views of larval creek chubsuckers, total 
length about 7.5 mm. Accurate identification of fish larvae 
is necessary for analysis of the effects of power plants on 
the environment. Photo by L Fuiman. 

has caused much concern. The goal of a study 
conducted by the New York Cooperative Fishery 
Research Unit was to prepare a comprehensive 
review of the widely scattered literature on the 
physical, chemical, and biological effects of 
dredging and spoil disposal in estuaries and to 
identify alternative methods of spoil disposal. Over 
500 scientific and technical articles were reviewed. 

Alterations of circulation patterns and uncon- 
trolled redistribution of sediments were the most 
important physical effects of dredging and open- 
water spoil disposal. Better understanding of 
erosion processes and mechanisms of sediment 
transport is needed before predictive modeling can 
be developed. 

Remobilization of contaminants appeared to be 
the most important chemical effect of dredging and 
spoil disposal. Such factors and processes as the 
sediment's clay fraction and organic content, 
oxidation-reduction potential, pH, bacterial flora, 
sulfur cycles, and iron cycles are known to influence 
remobilization of contaminants; however, no 
predictive models have been developed. 

Direct burial, habitat destruction, and con- 
taminant uptake, accumulation, and recycling were 
the most critical biological problems associated 
with dredging and spoil disposal. Careful timing of 
dredging and spoil disposal plus construction of 
diked spoil marshes and islands or transport of 
spoils to inland sites such as abandoned mines or 
landfill areas appear to be the best alternatives 
available at this time. 

During the past 2 years biologists with the New 

York Unit have greatly extended the period during 
which largemouth bass spawn. As a result, they had 
newly hatched bass available for study throughout 
the summer. Bass were removed from ponds shortly 
before the onset of spawning in mid-May, when 
water temperatures were 17° -18° C (62° -64° F), 
and were held in tanks under moderately crowded 
conditions. A strong flow of creek water at 
temperatures of 15° -22° C (59° -72° F) was 
maintained in each tank. When bass were then 
transferred to ponds with temperatures of about 
24° C (75° F), spawning occurred. Transfers were 
conducted throughout the summer; the last 
successful spawning occurred in early September. 
Besides extending the time available for research on 
the early life history of bass, this technique provides 
greater flexibility in fish culture by distributing 
production over a longer period. In addition, the 
availability of small bass over a longer season may 
be important for the stocking of fishing waters 
where natural reproduction has failed. 

North Carolina. — Intensive studies of the 
physical, chemical, and biological characteristics of 
an unaltered and an altered wooded swamp stream 
in northeastern North Carolina demonstrated 
substantial differences between the systems. 
Dissolved oxygen, for example, was relatively high 
in the channelized stream throughout the year, 
whereas low concentrations occurred in the 
nonchannelized stream in late summer and early 
winter. The species of fish in the two systems also 
differed. There were numerous swamp fish, herring, 
and fliers in the unchannelized stream but none in 
the channelized stream, and the several species of 
cyprinids that were found occurred only in the 
channelized area. 

In other studies, ultrasonic tracking of adult fish 
of several species in the vicinity of the intake 
structure of a nuclear power plant on the lower 
Cape Fear River did not produce evidence that the 
fish were attracted to the structure. Phylogenetic 
studies of North American ictalurids by karological 
and DNA techniques substantiated some of the 
conclusions of previous workers. Studies of 
swimming performances of juvenile spot, pinfish, 
and striped mullet demonstrated that sustained 
swimming time, time until exhaustion, and 
maximum swimming speed are increased by lower 
water velocities and higher temperatures. 

Ohio. — Whirling disease of trout, caused by the 
protozoan Myxosoma cerebralis, has spread ra- 
pidly over the United States since the mid-1950's 
and can become critical where young fish are 
concentrated in large numbers, as in hatcheries. 


Typical northern largemouth bass (above) and Florida 
largemouth bass (below) from a thermally enriched 
reservoir in Oklahoma. Oklahoma Cooperative Fishery 
Research Unit photo. 

Fish can carry the spores without showing the 
classic symptoms of whirling disease, and a 
secondary method of detection in fish-holding 
facilities to prevent introduction of the disease into 
natural waters is desirable. The objective of this 
study was to establish simple bioassay procedures 
for detection of the disease in holding facilities, to 
determine spore concentrations necessary for 
positive detection, and to study the effects of 
temperature, increased exposure time, and 
extraction technique on infectivity. Infection was 
noted in fish exposed to concentrations as low as 
8,581 spores per liter of water, but the method was 
not foolproof in fish exposed to concentrations as 
great as 139,744 spores per liter. Spores from fish 
carcasses were more infective than extracted spores 
in bioassay, and incubation times up to 240 days 
were required to maximize detection capability. 
The long incubation periods preclude widespread 
use of bioassay to detect the presence of Myxosoma 
cerebralis in fish-holding facilities. 

Oklahoma. — Study of a sparse population of 
largemouth bass in a 3,300-acre reservoir indicated 
that differences in lst-year growth, abundance, and 
production of several year classes were due largely 
to differences in water levels. Survival rates during 
the 1st year were higher than most comparable rates 
reported for denser populations of largemouth 

A nuisance growth of pondweeds was almost 
completely removed from a large pond to 
determine the effect of the removal on the growth of 

stunted bluegills. Removal of the plants resulted in 
fewer species of fish-food organisms through the 
loss of macroinvertebrates associated with plants. 
Increases in populations of several species that 
consumed detritus, however, resulted in greater 
consumption of food (by weight) by bluegills. As a 
consequence, the condition of the bluegills 
improved, but changes in rate of growth were only 

Possible effects of artificial destratification of 
small reservoirs on depth distribution and growth 
of fishes are still under investigation. To date, 
catches in gill nets have shown that black bullheads 
are more tolerant of anoxic conditions than are 
freshwater drum and white crappies, and that 
gizzard shad and channel catfish generally live in 
areas of the lake not strongly influenced by thermal 
and oxygen stratification. However, vertical 
distribution of all species was affected to some 
degree by reductions in oxygen. The most 
pronounced effect of artificial mixing on fish was 
the creation of an earlier autumnal partial 
circulation that allowed the fish to move to deeper 

The growth and survival of Florida and northern 
largemouth bass were compared in a reservoir that 
receives heated effluent and therefore may be 
suitable habitat for the Florida subspecies. Marked 
populations were stocked in 1974 and 1975 and 
were later sampled at seasonal intervals. Growth 
and survival were not significantly different except 
that overwinter survival of Florida bass was lower, 
especially during one severe winter. The distribution 
of the two subspecies differed according to water 
temperature, which suggests that in reservoirs 
located where winters are relatively mild, the 
introduction of Florida bass may be advantageous 
because they occupy habitat unused by northern 

Oregon. — Epizootics of bacteria-caused kidney 
disease have resulted in high mortalities of trout 
and salmon in hatcheries. Levels of antibodies for 
kidney disease in coho salmon at Big Creek 
Hatchery, Oregon, were higher in individuals with 
one particular blood protein-type (transferrin) than 
in fish with other types of transferrin. Because 
transferrin-type is determined genetically, we 
initiated a study to see whether fish with various 
genotypes of transferrin differed in their resistance 
to kidney disease. Coho salmon of known 
transferrin-type were infected with the disease. 
Mortalities were monitored, and it was found that 
resistance to kidney disease can be correlated with 
genotype. Treating the fish with various levels of 


iron did not alter the mortality rates for the various 
transferrin genotypes. However, results of the use 
of radioactive iron as a tracer suggested that 
infected fish increase their rate of iron storage. 
Coho salmon infected with kidney disease exhibit 
alterations in various blood chemistry characteristics 
throughout the progression of the disease. 
Consequently, coho salmon can be selectively bred 
for resistance to kidney disease, although environ- 
mental factors may nullify any resultant benefits. 

Introduction of artificially propagated steelhead 
trout into natural stream systems may influence 
resident wild populations. It is not known, 
however, whether there are genetic differences in 
growth rate or survival among offspring from 
matings of hatchery x hatchery, wild x wild, or 
hatchery x wild fish. Four natural streams and a 
hatchery pond in Oregon were each stocked with 
eggs or unfed fry from each of these three matings. 
A genetically determined biochemical marker was 
used so that fish from each type of mating could be 
distinguished. Hatchery fish mated with hatchery 
fish had the best survival and growth in the pond, 
whereas fish with two wild parents had the best 
survival in streams. Hatchery fish mated with wild 
fish had the best growth in natural waters. In 
conclusion, hatchery fish are genetically different 
from wild fish and, if the two interbreed, the stock 
recruitment of wild populations can be adversely 

The red-band trout, an undescribed species 
native to many small isolated streams in south- 
eastern Oregon, provides wild populations for 
recreational fishing. Data collected on the 
population size, age composition, growth, biomass, 
recruitment, fertility, and habitat of red-band trout 
in Threemile Creek indicated that production was 
extremely high. A terminal irrigation reservoir on 
the creek increased the total production of the 
system by at least 12 times. Terminal reservoirs 
might be considered management tools for 
improving trout populations in small streams; they 
provide larger trout than the streams would 
ordinarily produce. 

Pennsylvania. — Diurnal activity of wild adult 
smallmouth bass was studied during summer, fall, 
and winter. The bass spent most of their time (79- 
91%) in activities unrelated to movement. Almost 
all activity was restricted to areas where current 
velocity was low to moderate. Interactions with 
other smallmouth bass accounted for less than 1% 
of their time. Social organization in the population 
was based on a fairly stable order of dominance and 
on individual "exclusive use spaces" that apparently 

moved with the individual, changed shape, 
expanded or contracted, and were defended with 
varying intensity. Most feeding behavior was 
observed late in the day and probably continued 
into the night, after observations had ceased. 
Smallmouth bass apparently used several strategies 
to minimize expenditure of energy. 

Many attractive trout streams in the Appalachian 
Mountains are unproductive because of their 
acidity and low level of nutrients. Such streams 
might be managed for production of native trout or 
stocking of catchable trout by the use of limestone 
water treatment and other techniques. Although 
often intensified by boggy areas, the acidity appears 
to originate from rainfall and the geochemistry of 
the watersheds, coupled with the low buffering 
capacity of the water. A prototype limestone bed is 
being evaluated along with basic studies of water 

Brine shrimp have been proposed as a versatile 
and convenient starter food for "cool water" fish, 
especially northern pike, in hatcheries. Extensive 
tests led to guidelines for reliable production of 
brine shrimp on a routine basis and a large scale, 
without complex and expensive facilities. A 
solution of 0.5% rock salt in hard water proved 
most suitable as a medium. Different brands and 
ages of eggs varied greatly in hatchability. 

South Dakota. — Studies are being conducted to 
determine the life history of paddlefish in a section 
of the Missouri River in South' Dakota. The study 
area is a 93-km stretch of free-flowing river 
extending downstream from the lowermost dam on 
the Missouri River. Habitat is similar to that 
available to paddlefish in this region before it was 
influenced by man. Bank stabilization and river 
channelization have altered the river downstream 
from this area, and installation of bank stabilization 
structures will soon alter habitat in the study area. 

Paddlefish were visually observed from late 
spring to early fall and were located during the 
remainder of the year by netting and snag fishing. 
From late spring to early fall paddlefish were 
mainly found downstream from submerged 
sandbars, where the crests of the bars were 0. 1 to 
0.8 m below the surface, the river depth was 1.5 to 
4.5 m, and the current velocity was to 0.3 m/s. 
Nearly all large concentrations of paddlefish during 
this period were downstream from sandbars or in 
slow- or dead-water areas adjacent to a channel. 
Concentrations of paddlefish from late fall to early 
spring were primarily in slow- or dead-water areas 
more than 3 m deep and adjacent to the main 
channel of the river. 


Faculty and students from the Pennsylvania Cooperative Fishery Research Unit marking 8,000 rainbow trout to be 
stocked and studied in Stone Valley Lake. Photo by ft L Butler. 

Food of paddlefish was nearly 100%zooplankton. 
Feeding was clearly heaviest in spring and fall and 
nearly ceased from about July to September. 
Paddlefish appeared to feed continuously when 
levels of food consumption were high. Nonfood 
items composed 37 to 78% by volume of the total 
stomach contents. 

Measurement of length from the eye to the fork 
in the tail was determined to be more reliable in 
paddlefish than either total or fork length. Sexual 
dimorphism in both length and weight was 
determined to be statistically significant for fish in 
age groups II to XXII. Few mature females were 

observed. More than 35% of all paddlefish captured 
bore scars that apparently resulted from collisions 
with boats, injuries inflicted by snag hooks, or other 
damaging encounters. Of all fish tagged and 
recaptured, 67% traveled downstream and 26% 
upstream; 7% were caught near the site of release. 
Of the fish that traveled downstream, three had 
moved 680 to 780 km in 3 to 5 months. 

Tennessee. — Three of the studies conducted on 
the fisheries of Center Hill Reservoir were designed 
to model the fish population of the reservoir by the 
use of a computer, and the information thus 
obtained will be incorporated into an overall model 


of the fish population. Such a model should help 
fishery biologists manage fish populations in 

Some types of artificial shelters for fish have been 
successful in some reservoirs but not in others. A 3- 
year study was conducted in two reservoirs to 
evaluate "stake-bed" shelters. They increased 
fishing success for crappies in a reservoir with a 
fairly stable water level but not in one with a 
fluctuating water level. 

A survey was made of the fishes of the 
Cumberland River in the area of a proposed 
nuclear power plant. Other surveys will be made 
during the construction of the plant and after it is in 
operation to determine whether the fish population 
is affected by it. 

Utah. — Biochemical and genetic studies offish 
populations were emphasized. Two lactate dehy- 
drogenase isoenzymes of rainbow trout were 
examined kinetically. They were found to differ in 
reaction mechanism, binding constants, pH 
inhibition, and other factors. In another study, 
rainbow and cutthroat trout were found to differ in 
the number of electrophoretic hemoglobin 
fractions. The major fractions are being isolated 
and described. The data from these two studies will 
be useful to fish culturists in producing fish that 
more readily adapt to the environment. 

Studies of rare and endangered fish species of the 
Upper Colorado River are completed. Information 
is now available on the life history, movements, 
habitat needs, and ecological requirements of the 
Colorado squawfish and humpback sucker. These 
data will be useful for planning future water- 
development projects that may affect the remaining 
habitat of these endemic fish. 

The effects of channelization on the aquatic life 
of an intermountain river are being studied. The age 
composition, standing crop, and production of the 
principal fish (brown trout and mountain 
whitefish) and invertebrate populations in altered 
and unaltered sections of the Logan River were 
determined and compared. 

The Utah chub is the focus of studies dealing with 
the manipulation of undesirable fish populations. 
The chub frequently competes with western game 
fish for food and habitat. Preliminary studies are 
providing data on the biology and life history of the 
chub in a typical Utah reservoir. The action offish 
toxicants on the chub is also under investigation. 

Virginia. — Nuisance populations of an exotic 
aquatic plant, Egeria densa, hampered use of the 
1,093-ha Chickahominy Reservoir, southeast 
Virginia, for recreation and potable water. A 

mixture of diquat dibromide and potassium 
endothall was applied at 2.83 liters of each chemical 
per 0.4 surface ha. There were no measurable 
changes in water quality after treament, except for a 
general decrease in dissolved oxygen. No fish kills 
were observed. Oxygen consumption indicated that 
24 to 76% of the biomass of rooted plants was 
decomposed through oxidation in areas of heavy 
growth. Both herbicides had declined to low levels 
in the water 3 days after treatment and were 
undetectable 16 days after treatment. Anglers 
refrained from fishing while the treatment was in 
progress and believed the project increased fishing 
and boating enjoyment. 

In a second recently completed project, artificial 
reefs were evaluated in 8,I00-ha Smith Mountain 
Reservoir. Over 7,000 scrap tires and 400 Christmas 
trees were used to form four types of structures. 
Scuba surveys indicated that many species were 
seasonally associated with the reef structures. 
Various sunfish species used the reefs for shelter 
during the summer. Fewer fish were observed 
around the reefs during the colder months 
(December-February). Catfish deposited their eggs 
inside the tires, and gizzard shad and sunfish were 
observed grazing directly on the periphyton 
attached to reef substrate. In shelter-deficient 
nonflowing waters these artificial reefs effectively 
concentrated warmwater game and forage fish. 

Washington. — One of the recently completed 
projects dealt with methods for controlling the eye 
fluke, Diplostomum spathaceum, which affects 
trout in many Washington lakes. Salmonid species 
differed widely in resistance to the eye fluke: 
rainbow trout were the most resistant, followed by 
cutthroat trout, brook trout, and coho salmon. 
Larger fish were able to carry more eye flukes than 
were smaller fish of the same species. The survival 
time of rainbow trout and brook trout exposed to a 
controlled number of eye fluke cercariae was 
increased from twofold to more than threefold by 
immunization with a crude eye fluke extract. 

Another project was directed toward solving 
management problems affecting the kokanee 
salmon fishery in Lake Stevens, Washington. 
Streams entering and leaving the lake were 
surveyed regularly for spawning activity during the 
fall of 1975. 

Percentage survival of deposited eggs was 
estimated from counts of spawning kokanee and 
from trapping of out-migrant fry the next spring. 
Spawning areas in need of habitat improvement or 
special protection were identified. Although 
extensive spawning occurred in the lake outlet. 


Tending traps designed to capture kokanee fry migrating downstream from Lake Stevens, Washington. Photo by J. L. 

there was no upstream migration of newly emerged 
fry back into the lake the next spring. Electro- 
phoretic analysis of fry collected from the outlet 
and from tributary streams is being performed to 
determine whether outlet spawners were derived 
from a stock normally spawning in inlet streams. If 
so, the fry could be genetically predisposed toward 
downstream migration after emergence. 

Data were collected over a 1-year cycle on 
physical, chemical, and biological conditions in the 
spawning tributaries and in the lake. This 
information will be used to support efforts to 
counter the effects of progressive watershed 
urbanization and to maintain a viable kokanee 

Wisconsin. — Although angling for smallmouth 
bass in lakes in the north-central United States has 
been popular — sometimes even famous — for 
many years, the bass populations have not been 
studied intensively. A 2-year study of the 
smallmouth bass population and fishery in 850-acre 
Clear Lake, Wisconsin, was conducted to obtain 
information for use in fish management. Fish were 
caught in fyke nets, tagged, and released in spring 
and early summer, and anglers were interviewed in 
a creel survey during the fishing season. 

Annual mortality in a smallmouth bass population 
is typically 50 to 65%, but in Clear Lake the annual 
rate was 77%, most of it due to fishing. Anglers 

annually harvested 42% of the bass over 9 inches 
long. Creeled fish were small (average length, 8.7 
inches), and the catch rate of six bass for 100 hours 
of angling was not unusual for the species. We 
estimated that anglers caught 5 to 9 smallmouth 
bass per acre from a population of 22 bass per acre. 
We estimated that a limit of 12 to 14 inches in 
minimum length would cause the total weight of 
harvested bass to increase by 14%. In addition, the 
average size of fish in the population would 
increase, as would the catch and release rate. As a 
result of the study, a regulation limiting minimum 
length to 12 inches for smallmouth bass will be 
initiated next year on an experimental basis. 


Alabama. — A field study of the effects on wildlife 
of pine seed treated with endrin-arasan was 
conducted in southern Alabama. A 55-acre area 
was seeded with pine seed treated with 0.5% active 
endrin and 8.0% arasan, which has been employed 
to protect the seed from damage by insects, birds, 
and rodents. Fourteen captured bobwhites fitted 
with transmitters were released on the area after 
treatment. Seven of the instrumented bobwhites 
were found dead within 40 days, and radio contact 


Taming of carnivores through food handouts by workers on the Trans-Alaska Pipeline has led to wildlife nuisance 
problems and has altered patterns of wildlife mortality. This wolf is being offered food in the interests of photography by a 
pipeline worker at Isabell Pass camp. Photo by D. ft Klein. 

with the others was lost. Also, five bobwhites from 
one covey were dead within 3 days after release on 
the treated area. Many birds and mammals 
collected or found dead on the treated area 
contained endrin residues. 

Data on habitat use and seasonal movement were 
obtained from 105 eastern wild turkeys instru- 
mented with radio transmitters and from non- 
instrumented turkeys on four study areas in 
Alabama and one in Kentucky. The turkeys 
preferred a diversity of habitat types in their ranges 
and often made seasonal movements to meet their 
needs. Their movements and seasonal ranges 
indicated the importance of openings to turkeys. 
Hens moved farther in the spring than gobblers 
because of their special needs for nesting and 
brood-rearing habitat. Twelve to 25% of spring and 
summer habitat should consist of well-dispersed 
clearings in order to lessen the distance of spring 
dispersal of hens seeking open country to nest and 
raise poults. 

Alaska. — Aerial and ground counts of caribou 
in the vicinity of the Trans-Alaska Pipeline and the 
adjacent haul road on Alaska's North Slope show 
that females and calves use the areas close to the 
pipeline-road complex much less than the more 
distant areas. Behavioral observations indicate that 
cows with calves are more sensitive to highway 
traffic than bulls, which, during the peak of the 
insect season seek out elevated gravel pads, roads. 

and airstrips to obtain relief from insects, thus 
causing problems for highway traffic and landing 
aircraft. In general, carnivores and scavengers have 
been attracted to the construction camps and 
pipeline work pad, where food handouts by 

Studies of productivity of the dusky Canada goose on the 
Copper River Delta by personnel of the Alaska Cooperative 
Wildlife Research Unit have assessed the effects of the 
1964 earthquake on the welfare of the goose population. 
Photo by D. ft Klein. 


Inspecting Harris' hawk nest in saguaro. Photo by L. K. 

workers and improper garbage disposal have 
resulted in taming of wolves, bears, and arctic and 
red foxes. Highway mortality of foxes is high, 
apparently because they frequent the roads in 
anticipation of food handouts. Several bears that 
became nuisances and threatened human life 
around the construction camps had to be shot. The 
Alaska Board of Game has now imposed 
regulations making it illegal to feed animals 
throughout the State. Food wastes have also 
attracted many ravens, glaucous gulls, and ground 
squirrels to the camp areas. 

Studies of nesting ecology and productivity of 
the dusky Canada goose on Alaska's Copper River 
Delta, the sole breeding area for this race of goose, 
show that elevation of the delta by approximately 
3 m as a result of the 1964 earthquake has had 
pronounced effects on the nesting habitat of the 
geese. Although elevation of the land allowed 
mammalian predators freer access to the nesting 
areas, avian predation lessened as the invasion of 
shrubs and forbs along slough banks and into the 
now drier sedge meadows created more nesting 
cover. Raising of the vegetated portion of the delta 

Removing young Harris' hawk from nest for banding. 
Photo by L K. Sowls. 

Banding young Harris' hawk for return to nest. PhotobyL. 
K. Sowls. 

well above high tide levels has halted destruction of 
nests by storm-caused flood tides, which periodically 
have caused catastrophic losses in the past. The 
delta is still undergoing change, with shrubs and 
trees invading the open meadows much more 
rapidly than new marshlands are developing at the 
periphery of the delta. Consequently, over a period 
of time there may be a substantial reduction in 
available nesting habitat. 

Arizona. — In 1975 a controversy between 
falconers and protectionists over raptor regulations 


in Arizona demonstrated the need for more 
information on these species. That year, a study on 
the ecology and status of Harris' hawk was 
initiated. In an intensive search for nesting Harris' 
hawks, 134 active nest sites were found since 
January 1976, all within Maricopa, Pima, and 
Pinal counties. Harris' hawks are asynchronous 
nesters and have a long nesting season. Egg-laying 
dates ranged from January to September. Forty of 
the 157 nesting attempts at the 134 nest sites were 
failures. The following are examples of the 
productivity observed: Three clutches were laid by 
one female between January and June; the second 
clutch failed but five young were produced from the 
first and third clutches combined. Two other 
females each laid two clutches and each female 
produced seven young. Over 200 young were 
produced from the nests under observation. 

Study of bobcats in Arizona has been neglected 
until recently, when the value of predators became 
recognized by many people. In 1975 a study of the 
populations and food habits of bobcats was 
undertaken on the Three Bar Wildlife Area near 
Lake Roosevelt, Arizona. During 8 trap-nights, 
bobcats were captured, marked, and released, or 
were observed, in an area of about 29 km 2 . An 
estimated minimum density for the study area was 
0.28 bobcat/ km 2 , indicating a relatively high 
density. Attempts to attract bobcats to scent 
stations and visual attractant stations, where tracks 
could be counted, were unsuccessful. Rodents and 
lagomorphs were the most frequent foods (66.5 and 
37.5%) identified in 176 scats collected. Deer and 
javelina remains were identified in 2.8% and less 
than 1% of the scats, respectively. The frequency of 
rodent and lagomorph remains in the scats was not 
correlated with the numbers of prey censused, 
suggesting that these bobcats were selective in their 
feeding habits. 

Colorado. — An effort to estimate the number of 
mountain lions in a specified geographic area of 
Colorado was undertaken in 1974. The study site 
selected for the first season (winter 1974-75) lay 
between Canon City and Cripple Creek and 
covered approximately 900 km 2 (350 square miles). 
Two lions were marked and released on this area. 
Study of the 37 sets of tracks recorded on the area 
led to a population estimate of 15-25 lions, or 1 lion 
per 36-60 km 2 (14-23 square miles). The second 
segment of the study was carried out on a 1,950-km 2 
(750-square-mile) area between Canon City and 
Salida. Three of the 17 lions marked and released 
on this expanded study area were later treed (a total 
of 20 captures). An analysis of captures and of the 

Canadian Wildlife Service Biologist selects an egg from a 
whooping crane nest at Wood Buffalo National Park. One 
egg from each two-egg whooping crane nest was 
transplanted to the nest of sandhill crane foster-parents at 
Grays Lake, Idaho. Photo by E. Bizeau. 

135 sets of lion tracks recorded during this second 
season supported an estimate of 35-65 lions, or 1 
lion per 30-56 km 2 (12-21 square miles). It was 
concluded that the mountain lion population in 
Colorado is probably larger than was formerly 
estimated and that it probably is not in danger of 
being overharvested. 

Idaho. — The whooping crane, with its one 
tenuous migration route from the breeding area in 
Wood Buffalo National Park in the Northwest 
Territories of Canada to the line wintering spot at 
Aransas National Wildlife Refuge in Texas, has 
long teetered on the brink of extinction. In 1975 an 
experiment was launched to field-test the feasibility 
of employing greater sandhill cranes as foster- 
parents to hatch whooping crane eggs, rear the 
chicks to flight stage, take them south as family 
groups to winter in New Mexico, and return the 
young whoopers the next spring. The goal is 
establishment of a new population of whooping 
cranes that will nest in southeastern Idaho and 
winter in New Mexico. 

On May 29, 1975, 14 whooping crane eggs were 
transplanted from Wood Buffalo National Park to 
Grays Lake National Wildlife Refuge in Idaho. 
Nine eggs hatched. Four chicks survived and 
migrated with their foster-parents to the wintering 
area in New Mexico. All four families remained 
intact throughout the winter and returned on 


schedule to the San Luis Valley in south-central 
Colorado, the major stopping point in the spring 
and fall migration of the Rocky Mountain 
population of sandhill cranes. In April the whooper 
yearlings were left in the San Luis Valley to fend for 
themselves as the foster-parents returned to Grays 
Lake to begin a new nesting cycle. The orphaned 
whoopers slowly made their way north. None of the 
yearlings returned to their natal marsh at Grays 
Lake in the summer of 1 976. Three of the four were 
monitored at widely scattered summering locales in 
southeastern Utah, southeastern Idaho, and south- 
central Montana; the fourth yearling was not 
located. The first year of the project has 
demonstrated that whooper eggs can be successfully 
transplanted into sandhill crane nests and that the 
chicks are readily accepted and reared by the foster- 
parents. Parental care was excellent, and the 
whooper chicks readily adapted to the sandhill 
crane diet and living pattern. 

Iowa. — Organization, movements, distribution, 
and abundance of three herds of elk at Wind Cave 
National Park, South Dakota, were studied to 
permit more efficient management of elk through 
herd reduction by trapping. Elk were marked with 
ear flags, colored collars, or radio collars. Twenty 
bulls were captured by baiting a trap with salt, six 
calves by hand, and six cows by immobilization 
with syringe darts containing succinylcholine 


Radio collars, such as the one on this cow elk, were used to 
study herd movements and distribution of elk in Wind Cave 
National Park by the Iowa Cooperative Wildlife Research 
Unit. The study resulted in information that will aid Park 
personnel in herd management. Photo by K. L Varland. 

chloride. Use of a helicopter was most effective for 
delivering syringe darts to free-ranging cows. 

Marked elk were observed 713 times and located 
113 times by telemetry. Three relatively discrete 
herds of cows and calves — herd sizes of 170, 90, 
and 40 — were identified in the 44-square-mile 
park, occupying ranges of 8, 10, and 4.5 square 
miles, respectively. Bulls also seemed divided into 
three or more discrete herds. 

Elk were most readily observed during hours 
closest to sunrise and sunset. They generally fed in 
grassland areas and bedded in wooded areas. They 
preferred easterly or southerly slopes during most 
of the year and usually avoided steep slopes in all 
seasons. Aerial counts of elk in the Park probably 
underestimated the population. 

Reduction is not necessary for one of the three 
herds; this herd crosses the Park fence and spends 
time in the Black Hills National Forest, where it is 
subject to hunting. Definition of the ranges of the 
other two herds will indicate where traps can best be 
placed to reduce herd size. Knowledge of the 
seasonal distribution of elk within the Park helps 
Park managers to determine range use and to guide 
visitors through the Park. 

Louisiana. — Habitat evaluation is a major 
research responsibility. One study involving the 
bobwhite was conducted from September 1974 
through February 1976 to establish a population 
index in Louisiana and to observe related land use 
practices. Ten call index routes, each 30.5 km long 
and with 20 stops, were sampled throughout the 
State, and land use at each stop was recorded. Call 
index values ranged from 4.05 to 0.55 and peaked in 
June at an average of 1.57. Seventeen land-use 
associations in seven categories were recorded: row 
crops, small grains, pasture, residential, edge, 
woodland, and marsh. Four associations, partly or 
entirely woodland and pasture, supported 64.4% of 
the bobwhites along the routes. During the fall, 
flush counts along the survey routes yielded only 
three coveys, and these were on the routes with the 
highest call index. 

The Breeding Bird Survey was analyzed to 
determine whether it could be used as an index to 
bobwhite abundance. It was not significantly 
related to hunting success or land-use and could not 
be used as an index of bobwhite numbers in 
Louisiana. An analysis of bobwhite wings from 
hunter-killed bobwhites in 1974-75 and 1975-76 
indicated good reproduction, with 85 and 82% 
young, respectively. The cock to hen ratio was 
120:100 each season. Hunting pressure was not a 
limiting factor on bobwhites in Louisiana. The 


Helicopter used in drive-trap procedure for banding Canada geese on the west coast of Hudson Bay. Photo by R. A. 

apparent surplus of bobwhites surviving after the 
hunting season suggests that the number of 
bobwhites in the State should be increasing — but it 
is remaining stable. Current land use does not 
provide sufficient winter cover to allow bobwhite 
numbers to increase. 

Maine. — During the past 2 years measurements 
were made of Maine coyotes for taxonomic and 
management purposes. Mean weights of adult 
males and females were, respectively, 15.9 and 14.5 
kg; mean total lengths were 1,233 and 1,193 mm, 
and skull lengths were 205 and 195 mm. Pelage was 
of four general phases, being similar to those 
described for northeastern coyotes and eastern 
wolves and distinct from that of dogs. Seventy adult 
skulls from Maine and 44 from Quebec were 
analyzed taxonomically with the use of linear 
discriminant function. Of the specimens from 
Maine, 67 were identified as skulls of eastern 
coyotes and 3 as skulls of dogs. Maine coyotes seem 
to represent a wild hybridized form that became 
progressively purer as it moved eastward. The 
results of computerized study agree with earlier 
conclusions based on ocular examination and 
subjective judgment. 

Physiology of breeding female American eiders 
in Maine was studied from 1973 to 1975. Seasonal 
changes in body and organ weights were used to 
evaluate the relative status of nutrient reserves. 

Total carcass fat and protein levels, and blood 
characteristics, were also studied. Females 
established large nutrient reserves prior to egg 
laying and then virtually stopped feeding during 
laying and incubation. Body weights decreased 
32%; the loss was especially noticeable in weights of 
pectoral muscles. Failure to establish sufficient 
nutrient reserves may often limit renesting ability 
and probably also adversely affects nesting success 
of young adults through proportionally more nest 
desertions. The semistarvation of nesting females is 
an important stress factor that may, at times, be 
associated with heavy losses from epidemic diseases 
or parasites. Avian cholera was an important 
periodic cause of mortality among incubating 
Maine eiders. 

Massachusetts. — An ecological study of the 
fisher, using radiotelemetry, was conducted on the 
White National Forest in New Hampshire. Fishers 
are highly mobile, traveling throughout most of 
their home range (1,922 ha) within almost any 2- 
week interval. Adult males traveled the greatest 
distances, adult females the smallest, and subadults 
of both sexes moved intermediate distances. 
Neither home range size nor sharing of home areas 
was related to age or sex. Fishers are very active 
diurnally; during summer daylight hours they were 
active approximately 85% of the time. Fishers 
preferred wetland association (predominantly 


Exploring critical habitat of the grizzly bear in the Lincoln- Scapegoat Wilderness Area. Photo by K. L. Craighead. 

alder) and mixed softwood-hardwood forest types, 
and avoided open areas and pure hardwood stands. 
Food items most commonly found in the stomachs 
of fishers were mice, carrion, squirrels, birds, 
shrews, and fruit. Annual layers in the cementum of 
teeth were accurate indicators of age. 

Missouri. — The major breeding ground of the 
eastern prairie population of Canada geese is in 
Manitoba, between latitude 56° and 60° N and 
longitude 92° and 99° W, an area of about 59,700 
square miles. Band recoveries indicate that geese 
nesting north of this area belong to the tallgrass 
prairie population and those to the east to the 
Mississippi Valley population. Breeding populations 
surveyed within the major breeding area of the 
eastern prairie population increased nearly 40% 
between 1972 and 1975. Goose sightings from slow- 
flying aircraft must be multiplied by about 1.4 to 
reconcile them with ground-truth data obtained by 
observation from helicopters. Forty-four to 68% of 
estimated numbers of breeding pairs, 1972-75, were 
in tundra habitat south of Churchill, Manitoba, 
which made up less than 8% of the area surveyed. 

Research on the call behavior of mourning doves 
confirmed the findings of previous studies that 
pairing is the most important factor affecting 

calling. Unmated wild males called at significantly 
higher rates and had greater probability of being 
heard during 3-minute intervals than mated males. 
Although unmated males called at significantly 
higher rates when at least one other dove was 
calling, the rate did not increase as the number of 
calling doves increased. Other types of measurements 
showed that call rates of individual doves are not 
markedly affected by population densities, as 
asserted by earlier authors. 

Montana. — The Endangered Species Act 
prohibits Federal agencies from jeopardizing 
threatened or endangered species by disturbing or 
destroying critical habitat. Critical habitat for most 
species has not been defined or delineated. 
Conventional data-gathering techniques, combined 
with electronic scanning and digital data recording 
from satellites, were used in the Lincoln-Scapegoat 
Wilderness Area in Montana to define and analyze 
critical habitat for the grizzly bear. Radio 
monitoring and tracking of free-roaming animals, 
using thematic satellite imagery maps to record 
movement, distribution, habitat preferences, and 
behavior, are now feasible and will open new vistas 
in wildlife research and management. 

Scats collected throughout the year on the 


National Bison Range indicated that voles were the 
most important single food of coyotes. Native 
ungulates (especially fawns), insects, seeds, berries, 
and cattle (presumably carrion) were seasonally 
important. Although coyote predation may be a 
major cause of fawn mortality, increased numbers 
of coyotes did not always result in a decrease in the 
number of fawns per doe. Individual coyotes adept 
at finding and killing fawns could be more 
dangerous than a large number of less proficient 
coyotes. Proximity of coyote dens correlated with 
mortality of pronghorn fawns in the three herds on 
the Range. 

New York. — Recent studies indicate that 
recreational opportunities in New York State are 
rapidly disappearing as landowners react against 
misuse of their properties by hunters, operators of 
snowmobiles, and other recreationists. A joint 
effort between the New York Department of 
Environmental Conservation and the Unit was 
undertaken in 1972-73 to examine levels of posting 
against trespass, reasons for posting, and related 
landowner attitudes in 28 of the same rural New 
York towns studied in 1963. The results of the new 
study were noteworthy. In 1963, 5.5 million acres of 
private land were posted; by early 1973, 9.2 million 
acres were posted, a 65% increase in the last 10 
years. Moreover, if the trend evident from 1963 to 
1973 were continued to 1993, virtually all private 
land in the State would be closed to public access. 

If the escalating conflict between landowners and 
recreationists is to be eased, comprehensive 
programs must be undertaken to educate the 
snowmobile operator, the hunter, and other users 
of private lands to change their behavior and image. 
Recreationists and private landowners will both 
need the protection of mutually advantageous 
management programs such as New York's Fish 
and Wildlife Management Act, which encourages 
and assists private landowners in opening their 
lands to the hunting and fishing public. If these 
programs are to be effective, cooperation from both 
public agencies and industry will be required. 

Ohio. — Leg muscles and livers from road-killed 
white-tailed deer and cottontail rabbits collected 
during 1971-75 in west-central Ohio were analyzed 
for cadmium, lead, and mercury content. Con- 
centrations of these elements were significantly 
higher in livers than in muscles for both species. 
Rabbit livers contained significantly higher levels 
than did deer livers. Concentrations in body tissues 
were generally well below guidelines recommended 
by the U.S. Food and Drug Administration and 
consequently posed no threat to human consumers. 

Lead levels in vegetation collected near highways 
were directly related to volume of traffic and were 
inversely correlated with distance from the 
highways. Variations in cadmium levels in plants 
appeared related to the cadmium content of the soil 
and not to distance of the plants from highways. 
Mercury levels differed between vegetative types 
and areas and seasons of collection, but no specific 
pattern was noted. 

The only known method for accurately aging 
adult Canada geese is by banding at a known age. 
Decalcified and stained 14-micron sections of all 
wing and leg bones from 19 known-age (1-7 years) 
geese from Ohio were examined to determine the 
feasibility of aging geese by counting annuli in bone 
periosteum. Periosteal annuli were present in all 
bones examined, but the number was not consistent 
for the various sections of the bones examined. 
Birds 1-2 and 5-7 years old were consistently over- 
and under-aged, respectively. This technique was 
concluded to be infeasible for aging Canada geese. 

Oklahoma. — Sixteen skull and tooth measure- 
ments taken on each of 138 wild Canis collected 
during 1975-76 were compared with those from 
museum specimens to detect temporal changes in 
Canis taxonomy. Records of depredation ex- 
perienced by the cattle industry were compared 
with average Canis body size and extent of coyote x 
dog hybridization within Oklahoma. Size char- 
acteristics of Canis appear stable except to the 
southeast, where red wolf x coyote genetic influence 
is declining. Losses of cattle appear to be positively 
related to the larger size of canids in the southern 
and southeastern counties. No correlation was 
found between the prevalence of coyote x dog 
hybridization and predation on cattle. 

A project was initiated to determine the causes of 
fawn mortality in white-tailed deer on the Wichita 
Mountains National Wildlife Refuge and on the 
Fort Sill Military Reservation. Thirty-five fawns, 
1 to 28 days old, were captured and fitted with radio 
transmitters. Their average annual mortality 
proved to be 88%. Predation by coyotes and 
bobcats caused 97% of the observed mortality. 
Eighty-three percent of the mortality occurred by 
the time fawns were 60 days old. Thus, predators 
killed a substantial proportion of the fawn 
population even though deer densities were low (8 
deer/km 2 ). 

Oregon. — The Oregon and Idaho Cooperative 
Wildlife Research Units, in cooperation with the 
University of Washington, completed in 2 years the 
first systematic inventory of wildlife and wildlife 
habitat resources along the Columbia and Snake 


Rocket net being fired to capture band-tailed pigeons. Research on band-tailed pigeons, conducted in Oregon, is 
directed toward determination of survival rates and age structure of this popular Pacific Coast game bird. Photo by 
M. F. Passmore. 

rivers. Special attention was directed toward 
identifying the impact of fluctuating pool levels to 
accommodate "power peaking" — the coordinated 
release of water by the many dams in the system to 
meet changing energy demands on a daily, weekly, 
and seasonal basis. Breeding waterfowl and aquatic 
furbearers, often concentrated in relatively short 
stretches of river immediately below some dams, 
are especially vulnerable to the disturbances of 
power peaking. The Great Basin Canada goose may 
serve as an indicator species for the negative impact 
of power peaking, as nesting, feeding, and brooding 
areas are all adversely affected. 

Pennsylvania. — As part of a comprehensive 
study of black bears, blood samples were collected 
from 44 immobilized bears captured in northeastern 
Pennsylvania between October 1972 and November 
1973 (one, two, three, and four samples were 
collected from 31, 7, 3, and 3 individuals, 
respectively, a total of 66 samples). The samples 
provided information on 23 blood chemistry and 
hematology parameters. The resulting data were 
statistically analyzed to establish normal blood 
values and to determine their relationship to sex, 
age, or season. 

Our data indicate that female bears tend to be 
anemic and to have lower levels of calcium in the 
blood. This tendency toward anemia may be caused 
by the demands of pregnancy and lactation, 

because females nurse their cubs for 2 or more 
months during winter dormancy. They do not eat 
during this period, and thus minerals lost during 
late pregnancy and lactation cannot be replaced. 
Cubs and yearlings also tend to be anemic and may 
have a higher turnover of red blood cells than 
adults. Advancing age is accompanied by an 
increase in blood cholesterol, suggesting that food 
habits or the utilization of foods may alter with age. 
Increases in total protein and globulin with age may 
indicate increased antibody production in older 
bears. Seasonal differences in certain red blood cell 
indices and in glucose suggest heightened activity of 
the blood-producing organs and increased 
ingestion of high-energy foods during the 
predenning period. Some individuals demonstrate 
abnormal blood profiles, which are attributable to 
various possible causes including dehydration, 
stress, tissue damage, renal dysfunction, and 

South Dakota. — The flock of giant Canada 
geese in northeastern South Dakota numbered 
about 2,000 birds in 1973. The South Dakota 
Department of Game, Fish and Parks has a 
management goal of 5,000 birds for that flock. 
Although public sentiment favored this goal, some 
farmers opposed it because waterfowl depredations 
on small grain crops would increase. It appeared 
that attitudes of farmers might be the major factor 


Three ferruginous hawk nestlings at their nest on top of a 
large butte in northwestern South Dakota. The nest, 
approximately 2 m in height, has been used for a number of 
years. Photo by C. Blair. 

prohibiting management from reaching the goal of 
5,000 geese. 

Four hundred farmers in northeastern South 
Dakota were interviewed in 1974 and 1975 to 
measure their attitudes toward expansion of the 
flock. Eighty-six percent of the interviewed farmers 
favored the expansion. Only 6% of the farmers 
complained about the geese, even though 23% of 
them had crops damaged by geese. Percentage 
occurrence of complaints and of crop damage was 
influenced by distance of goose concentration areas 
from farms. Farmers whose land was adjacent to 
goose concentration areas had a lower tolerance for 
geese than those farther away but retained 
relatively positive attitudes toward the geese and 
flock expansion. Farmers' complaints about crop 
damage concerned geese eating small grains, 
trampling small-grain swaths, grazing shoots of 
small grains in spring, and attracting trespassing 

Productivity of the goose flock was also 
measured and was comparable to success reported 
for flocks of giant Canada geese in other parts of the 
country. Desertion was the most common cause of 
nest failure. Predation and flooding did not appear 
to be major limiting factors in nest success. Nest 
success appeared adequate to support or expand 
the flock, indicating that the goal of 5,000 geese is 
probably realistic. 

Utah. — A 2-year greenhouse investigation at 
Utah State University to determine the effects of 
fertilizers on Potamogeton pectinatus, Ruppia 
maritima, and Chara has been completed. A 
completely randomized block design with six 
treatments was used: control; 28, 56, 112 kg N/ha; 
56 kg N and 56 kg P/ha; and 56 metric tons sewage 

sludge/ha. Analysis of variance and covariance, 
and regression techniques were employed to 
determine growth response in terms of production, 
height, and dry weight of shoots, reproduction, and 
tissue nutrients. Nitrogen fertilization improved the 
growth of Potamogeton and Ruppia. Phosphate 
fertilization improved only the growth of 
Potamogeton. Large amounts of nitrogen and 
phosphate fertilizer inhibited the growth of Chara. 
Nitrogen yields from tissue analysis increased 
linearly with added treatment nitrogen in 
Potamogeton and Ruppia. Phosphorus in the 
sewage sludge was believed to have increased 
plant height and dry weight but also produced 
heavy growth of algae. Soil and water analyses 
showed losses of ammonia, nitrate, and phosphorus 
by the end of the experiments. Recommendations 
were made for study of fertilization in a spring-fed 

Virginia. — Data on the effects of stream 
channelization on riparian wildlife populations and 
their habitats along three streams were collected 
from January 1975 through July 1976. The streams 
studied were channelized 2, 5, and 9 years prior to 
the investigation. The study was designed to 
measure the recovery of wildlife populations at the 
successional stages that developed after channelization. 
The relative composition of vegetation and the 
relative abundance of small mammals and birds 
were determined for each study site. Populations of 
mammals were estimated each year by snap- 
trapping and livetrapping 1.1 ha on each study site. 
Bird abundance was estimated twice each year by 
winter transect counts and breeding bird inventories. 
Indices of species diversity for vegetation, small 
mammals, and birds increased from the youngest to 
the oldest channelized stream. Channelization 
appeared to affect wintering populations less than 
breeding populations of birds. Bird diversity and 
density were significantly lower along the younger 
channelized streams, where vegetative complexity 
had been more recently reduced by removal of trees 
and shrubs. During the breeding season, parulids 
appeared most affected by stream alteration. 
Relative changes in diversity values of small 
mammal and breeding bird species between the 3- 
and 6-year-old channelized streams indicated that 
small mammal populations recovered more quickly 
than breeding bird populations. The small 
difference found in mammal and breeding bird 
diversities between the 10-year-old channelized 
stream and the unchannelized stream strongly 
suggested that 10 years after channelization, 
riparian small mammal and breeding bird 


populations were approaching those of the 
unchannelized (control) stream. Both breeding bird 
and small mammal populations recovered as the 
complexity of the riparian vegetation increased. 
Information gained from this study may be used to 
predict the impact of channelization and may thus 
contribute to rational land management by State 
and Federal agencies and private landowners. 

Wisconsin. — The coot is one of the most 
important migratory game birds in Wisconsin, but 
few data on coot populations are presently 
available. The need for data will probably escalate 
as harvests and harvest rates of coots increase. In 
1974-76, approximately 5,000 coots were banded in 
southeastern Wisconsin. Band recoveries to date 
suggest that most of the harvest in Wisconsin 
occurs in the southeastern portion of the State and 
along the Mississippi River. Coots from Wisconsin 
apparently winter along the Gulf of Mexico and the 
Atlantic Coast. 

Deer cause damage to apple orchards in many 
States, and Wisconsin is one of nine States that 
reimburses orchardists for apple losses. Approxi- 
mately 77% of the apple growers reported damage 
by deer. Browsing of buds was the type of damage 
most frequently reported. The physical damage to 
mature apple trees can now be adequately 
measured, but the relationship between browsing 
and subsequent fruit production is unknown. In 
1975, studies to define this relationship and to 
develop indices to deer damage in orchards were 
begun. Preliminary work suggests a correlation 
between deer damage and pellet group counts 
associated with individual trees. Feeding trials with 
penned deer indicate that deer prefer terminal apple 
buds to lateral or axillary buds. Simulated 
browsing experiments and measurements of 
damage and subsequent production in three 
orchards are still under way. 



Abler, W. A., D. E. Buckland. R. L. Kirkpatrick. 
and P. F. Scanlon. 1976. Plasma progestins and 
puberty in fawns as influenced by energy and protein. 
Journal of Wildlife Management 40(3):442-446. 

Adams, B. L., W. S. Zaugg, and L. R. McLain. 

1975. Inhibition of salt water survival and Na-K- 
ATPase elevation in steelhead trout (Salmo gairdneri) 
by moderate water temperatures. Transactions of the 
American Fisheries Society 104(4):766-769. 

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(as of June 15, 1977) 

Central Offices 

(Mailing Address: U.S. Department of the Interior, 
Fish and Wildlife Service, Washington, D.C. 20240) 
Division of Wildlife Research 
Richard N. Smith, Acting Chief 
Division of Fishery Research 
Dr. James A. McCann, Chief 
Division of Habitat Preservation 
Nelson B. Kverno, Chief 

Major Research Facilities 

Atlantic Salmon Investigations 

Dr. Robert E. Lennon, Chief 

319 Murray Hall 

University of Maine 

Orono, ME 04473 

Denver Wildlife Research Center 

Dr. Charles M. Loveless, Director 

Building 16, Federal Center 

Denver, CO 80225 

Eastern Fish Disease Laboratory 

Dr. Kenneth Wolf, Director 

R.D. 3, Box 41 

Kearneysville, WV 25430 

Editorial Office 

William R. Dryer, Technical Editor 

U.S. Fish and Wildlife Service 

Aylesworth Hall, CSU 

Fort Collins, CO 80523 

Fish Control Laboratory 

Dr. Fred P. Meyer, Director 

P.O. Box 818 

La Crosse, WI 54601 

Fish Farming Experimental Station 

Dr. Harry K. Dupree, Director 

P.O. Box 860 

Stuttgart, A R 72160 

Fish Genetics Laboratory 

Dr. Raymond C. Simon, Director 

Beulah, WY 82712 

Fish-Pesticide Research Laboratory 

Dr. Richard A. Schoettger, Director 

Route 1 

Columbia, MO 65201 

Great Lakes Fishery Laboratory 

Dr. Joseph H. Kutkuhn, Director 
1451 Green Road 
Ann Arbor, MI 48105 

Migratory Bird and Habitat Research Laboratory 

Dr. Fant W. Martin, Director 
U.S. Fish and Wildlife Service 
Laurel, MD 20811 

National Fish and Wildlife Health Laboratory 

Dr. Milton Friend, Director 
6101 Mineral Point Road 
Madison, WI 53706 

National Fish and Wildlife Laboratory 

Dr. Clyde J. Jones, Director 
U.S. National Museum 
10th and Constitution Avenue, NW 
Washington, D.C. 20560 

National Reservoir Research Program 

Robert M. Jenkins, Director 
113 South East Street 
Fayetteville, AR 72701 


Northern Prairie Wildlife Research Center 

Dr. W. Reid Goforth, Director 
Box 1747 

Jamestown, ND 58401 
Patuxent Wildlife Research Center 

Dr. Lucille F. Stickel, Director 
U.S. Fish and Wildlife Service 
Laurel, MD 20811 

Pyramid Lake Project 

Earl A. Pyle, Leader 
U.S. Fish and Wildlife Service 
63 Keystone Avenue, Room 207 
Reno, NV 89503 

Southeastern Fish Cultural Laboratory 

Dr. Blake F. Grant, Director 

Marion, AL 36756 

Tunison Laboratory of Fish Nutrition 

Dr. Gary L. Rumsey, Director 

Cortland, NY 13045 

Western Fish Disease Laboratory 

Thomas Parisot, Director 

Building 204, Naval Support Activity 

Seattle, WA 98115 

Cooperative Fishery Research Units 

Auburn Univ., Auburn, AL 36830 

Dr. John S. Ramsey, Leader 

Univ. of Arizona, Tucson, AZ 85721 

Dr. Jerry C. Tash, Leader 

Humboldt State Univ., Areata, CA 95521 

Dr. Roger A. Barnhart, Leader 

Colorado State Univ., Fort Collins, CO 80521 

Dr. William J. McConnell, Leader 

Univ. of Georgia, Athens, GA 30601 

Dr. Robert E. Reinert, Leader 

Univ. of Hawaii, Honolulu, HI 96822 

Dr. John A Maciolek, Leader 

Univ. of Idaho, Moscow, ID 83843 

Dr. Theodore C. Bjornn, Leader 

Iowa State Univ., Ames, IA 50010 

Dr. Robert J. Muncy, Leader 

Louisiana State Univ., Baton Rouge, LA 70803 

Dr. Charles F. Bryan, Leader 

Univ. of Maine at Orono, Orono, ME 04473 

Dr. Richard W. Hatch, Leader 

Univ. of Massachusetts, Amherst, MA 01002 

Dr. Roger J. Reed, Leader 

Univ. of Missouri, Columbia, MO 65201 

Dr. Richard O. Anderson, Leader 

Montana State Univ., Bozeman, MT 59715 

Dr. Richard W. Gregory, Leader 

Cornell Univ., Ithaca, NY 14850 

Dr. John G. Nickum, Acting Leader 

North Carolina State Univ., Raleigh, NC 27607 

Dr. Melvin T Huish, Leader 

Ohio State Univ., Columbus, OH 43210 

Dr. Bernard L. Griswold, Leader 

Oklahoma State Univ., Stillwater, OK 74074 

Dr. O. Eugene Maughan, Leader 

Oregon State Univ., Corvallis, OR 97331 

Dr. Carl B. Schreck, Asst., Leader 

Pennsylvania State Univ., University Park, PA 16802 

Dr. Robert L. Butler, Leader 

South Dakota State Univ., Brookings, SD 57006 

Dr. Donald C. Hales, Leader 

Tennessee Technological Univ., Cookeville, TN 38501 

Dr. R. Don Estes, Leader 

Utah State Univ., Logan, UT 84321 

Dr. Richard S. Wydoski, Leader 

Virginia Polytechnic Institute and State Univ., 

Blacksburg, VA 24061 
Dr. Garland B. Pardue, Leader 
Univ. of Washington, Seattle, WA 98105 
Dr. Richard R. Whitney, Leader 
Univ. of Wisconsin, Stevens Point, WI 54481 
Dr. Daniel W. Coble, Leader 

Cooperative Wildlife Research Units 

Auburn Univ., Auburn, AL 36830 

Dr. Daniel W. Speake, Leader 

Univ. of Alaska, Fairbanks, AK 99701 

Dr. David R. Klein, Leader 

Univ. of Arizona, Tucson, AZ 85721 

Dr. Lyle K. Sowls, Leader 

Colorado State Univ., Fort Collins, CO 80523 

Dr. Kenneth R. Russell, Leader 

Univ. of Idaho, Moscow, ID 83843 

Dr. Maurice G. Hornocker, Leader 

Iowa State Univ., Ames, IA 50010 

Dr. Robert B. Dahlgren, Leader 

Louisiana State Univ., Baton Rouge, LA 70803 

John D. Newsom, Leader 

Univ. of Maine at Orono, Orono, ME 04473 

Howard L. Mendall, Leader 

Univ. of Massachusetts, Amherst, MA 01002 

Dr. Wendell E. Dodge, Leader 

Univ. of Missouri, Columbia, MO 65201 

Dr. Thomas S. Baskett, Leader 

Univ. of Montana, Missoula, MT 59801 

Dr. John Craighead, Leader 

Cornell Univ., Ithaca, NY 14853 

Dr. Milo E. Richmond, Leader 

Ohio State Univ., Columbus, OH 43210 

Dr. Theodore A. Bookhout, Leader 

Oklahoma State Univ., Stillwater, OK 74074 

Dr. Paul A. Vohs, Jr., Leader 

Oregon State Univ., Corvallis, OR 97331 

Dr. E. Charles Meslow, Leader 

Pennsylvania State Univ., University Park, PA 16802 

Dr. James S. Lindzey, Leader 

South Dakota State Univ., Brookings, SD 57006 

Dr. Raymond L. Linder, Leader 

Utah State Univ., Logan, UT 84322 

Dr. David R. Anderson, Leader 

Virginia Polytechnic Institute and State Univ., 

Blacksburg, VA 24061 
Dr. Burd S. McGinnes, Leader 
Univ. of Wisconsin, Madison, WI 53706 
Dr. Donald H. Rusch, Leader 



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Sharp-tailed grouse (above) and sage grouse (below) occupy areas that may be disturbed by future strip mining 
for coal in the West. Sage grouse return to traditional areas for breeding each year. Photo by D. E. Biggins. 

The U.S. Fish and Wildlife Service is conducting research on polar bears in Alaska. Animals are marked to obtain 
information on movements and populations. This female bear (estimated to weigh 350 pounds) and cub (15 pounds) 
were captured in April 1976 and fitted with numbered ear tags for individual identification. This program will provide a 
basis for evaluating the status of polar bears in Alaska. Photo by A. L. Kolz. 

Male polar bear approximately 40 miles north of Barrow, Alaska, being instrumented with a 164-megahertz, mortality- 
sensing transmitter. The bear was estimated to weigh about 900 pounds. Photo by A. L Kolz.